We gather from this passage why the angel appeared to the Prophet in the third year of Cyrus. He says, he was then in the greatest sorrow; and what was the cause of it? At that period we know an interruption of the work of rebuilding the temple and city to have taken place. Cyrus was gone to a distance; he had set out for Asia Minor, and was carrying on war with the Scythians. His son Cambyses was corrupted by his couriers, and forbade the Jews to proceed with the rebuilding of their city and temple. The freedom of the people might then seem in vain. For God had promised the Jews in glowing language a return to their country with their standards unfurled. Besides this, we know the splendid language of the prophets respecting the glory of the second temple. (Isaiah 52:12; Haggai 2:9, and elsewhere.) When thus deprived of all opportunity of rebuilding their temple, what could the Jews determine except that they had been deluded after returning to their country, and God had made a shew of disappointing expectations which had turned out a mere laughing-stock and deception? This was the cause of the grief and anxiety which oppressed the holy Prophet. We now understand why he mentions the third year of Cyrus, as the circumstances of that period, even at this day, point out the reason of his abstinence from all delicacies. He says, He was in affliction for three weeks of days The Hebrews often use the phrase weeks or times of days for complete periods. Very possibly, Daniel uses the word "days" here, to prevent a mistake which might easily occur through his so lately speaking of weeks of years. The distinction is thus more clearly marked between the seventy weeks of years previously explained, and these three weeks of days here mentioned. And the angel appears to have dwelt purposely on the completion of these three weeks, as this was the third year of King Cyrus's reign. He says, He did not eat delicate bread, and he abstained from flesh and wine, implying his practice of uniting fasting with mourning. The holy Prophet is here represented as freely using flesh and other food, while the Church of God remained in a state of tranquillity; but when there was danger, lest the few who had returned home should be diminished, and many were still suffering at Babylon those grievous calamities to which they were subject during their exile from neighboring enemies, then the Prophet abstained from all delicacies. In the beginning of this book, he had stated the contentment of himself and his companions with bread, and pulse, and water for meat and drink. This statement is not contrary to the present passage. There is no necessity to fly to that refinement, which allows an old man to use wine, which he never touched in his youth and the flower of his age. This comment is far too frigid. We have shewn, how at the beginning of his exile the only reason for the Prophet's abstaining from the delicacies of the palace, was the desire of preserving himself free from all corruption. For what was the object of the king's designing shrewdness in commanding Daniel and his companions to be treated thus daintily and luxuriously? He wished them to forget their nation by degrees, and to adopt the habits of the Chaldeans, and to be withdrawn by such enticements from the observance of the law, from the worship of God, and from the exercises of piety. When Daniel perceived the artful manner in which he and his companions were treated, he requested to be fed upon pulse, he refused to taste the king's wine, and despised all his dainties. His reason, therefore, concerned the exigencies of the times, as I then pointed out at full length. Meanwhile, we need not hesitate to suppose, that after giving this proof of his constancy, and escaping from these snares of the devil and of the Chaldean monarch, he lived rather freely than frugally, and made use of better bread, and fresh, and wine than before. This passage, then, though it asserts his abstinence from flesh and wine, need not imply actual fasting. Daniel's method of living was clearly after the common practice of the Chaldeans, and by no means implies the rejection of wine, or flesh, or viands of any kind. When he says, he did not eat delicate bread, this was a symbol of sorrow and mourning, like abstinence from flesh and wine. Daniel's object in rejecting delicate bread and wine during those three weeks, was not merely the promotion of temperance, but suppliantly to implore the Almighty not to permit a repetition of those sufferings to his Church under which it had previously labored. But I cannot here treat at any length the object and use of fasting. I have done so elsewhere; even if I wished to do so, I have no time now. To-morrow, perhaps, I may say a few words on the subject, and then proceed with the rest of my observations.

In those days I Daniel was mourning - I was afflicting myself; that is, he had set apart this time as an extraordinary fast. He was sad and troubled. He does not say on what account he was thus troubled, but there can be little doubt that it was on account of his people. This was two years after the order had been given by Cyrus for the restoration of the Hebrew people to their country, but it is not improbable that they met with many embarrassments in their efforts to return, and possibly there may have sprung up in Babylon some difficulties on the subject that greatly affected the mind of Daniel. The difficulties attending such an enterprise as that of restoring a captured people to their country, when the march lay across a vast desert, would at any time have been such as to have made an extraordinary season of prayer and fasting proper.
Three full weeks - Margin, "weeks of days." Hebrew, "Three sevens of days." He does not say whether he had designedly set apart that time to be occupied as a season of fasting, or whether he had, under the influence of deep feeling, continued his fast from day to day until it reached that period. Either supposition will accord with the circumstances of the case, and either would have justified such an act at anytime, for it would be undoubtedly proper to designate a time of extraordinary devotion, or, under the influence of deep feeling, of domestic trouble, of national affliction, to continue such religious exercises from day to day.

I - was mourning three full weeks - The weeks are most probably dated from the time of the termination of the last vision. Calmet proves this by several reasons.

In those days I Daniel was mourning,.... Either on account of what had been revealed to him in the last vision or prophecy of the seventy weeks; by which it appeared what wickedness the people of the Jews would be guilty of in cutting off the Messiah; and what desolations would come upon their land, city, and temple, for such usage of him: as also because of the present case of his people; many of them continuing in the country of Babylon, when they had liberty to return to their land: or because of the hinderance the Jews met with in rebuilding their city and temple, who had returned thither; of which Daniel had an account, and which caused him to mourn in secret: and so he continued
three full weeks; or, "three weeks of days" (c); so called, to distinguish them from weeks of years, mentioned in the preceding chapter.
(c) "tribus hebdomadibus dierum", Munster, Calvin, Tigurine version; "trium hebdomadarum diebus", V. L. Pagninus, Montanus, so Junius & Tremellius, Medus.

mourning--that is afflicting myself by fasting from "pleasant bread, flesh and wine" (Daniel 10:3), as a sign of sorrow, not for its own sake. Compare Matthew 9:14, "fast," answering to "mourn" (Daniel 10:15). Compare 1-Corinthians 8:8; 1-Timothy 4:3, which prove that "fasting" is not an indispensable Christian obligation; but merely an outward expression of sorrow, and separation from ordinary worldly enjoyments, in order to give one's self to prayer (Acts 13:2). Daniel's mourning was probably for his countrymen, who met with many obstructions to their building of the temple, from their adversaries in the Persian court.

Daniel 10:2, Daniel 10:3 introduce the following revelation by a statement of the occasion of it. ההם בּימים refers back to the date named in Daniel 10:1. The ימים after שׁבעים does not serve to designate the three weeks as common day-weeks, in contrast to the שׁבעים of Daniel 9:24., but is an accusative subordinated to the definition of time which expresses the idea of continuance: three weeks long, or three whole weeks, as Genesis 41:1; cf. Gesen. Gramm. 118, 3. For three weeks Daniel mourned and fasted, i.e., abstained from the usual food. חמות לחם, precious food, delicacies; but Hv., v. Leng., Maur., Hitz., and Kran. interpret it of leavened bread, so called in contrast to the unleavened paschal bread, the bread of affliction (Deuteronomy 16:3). But this contrast is not well founded, for the מצּות (unleavened cakes) of the passover was not (notwithstanding Deuteronomy 16:3) bread of sorrow, but pure, holy bread, which Daniel did not eat, in opposition to the law, for three weeks. לחם is not to be limited to bread in its narrower sense, but denotes food generally. Flesh and wine are festival food, Isaiah 22:13; Genesis 27:25, which is not had every day. The anointing with oil was the sign of joy and of a joyous frame of mind, as with guests at a banquet, Amos 6:6, and was intermitted in the time of sorrow; cf. 2-Samuel 14:2. Fasting, as an abstaining from the better sustenance of common life, was the outward sign of sorrow of soul.
According to Daniel 10:4, Daniel mourned and fasted in the first month of the year, the month in the middle of which the paschal feast was kept, in which Israel celebrated their deliverance from their state of slavery in Egypt and their advancement to be the people of God, and were joyful before their God. On the 24th day of this month occurred the Theophany (Daniel 10:4.), with which, however, his fasting came to an end. According to this, it appears that he fasted from the third to the twenty-third of the month Nisan; thus it began immediately after the feast of the new moon, which was kept for two days (cf. 1-Samuel 20:18., 27, 34 with 6:29; Daniel 2:19). Thus Hv. and Hitzig conclude; while v. Leng. and Maurer argue, from Daniel 10:13, that between the time of fasting and the appearance of the angel an interval elapsed, consequently that Daniel fasted from the first to the twenty-first of the month Nisan. But from Daniel 10:13 nothing further follows than that the angel was detained twenty-one days; so that the question as to the beginning and the end of the fast is not certainly answered from the text, and, as being irrelevant to the matter, it can remain undecided. More important is the question as to the cause of such long-continued great sorrow, which is not answered by the remark that he was thus prepared for receiving a divine revelation. According to Daniel 10:12, Daniel sought הבּין, i.e., understanding as to the state of the matter, or regarding the future of his people, which filled him with concern. The word about the restoration of Jerusalem which he had received through the angel Gabriel in the first year of Darius (Daniel 9) had come to pass since that revelation in the first year of Cyrus, but had had only little effect on the religious lukewarmness of the majority of the people. Of the whole people only a very small portion had returned to the land of their fathers, and had begun, after restoring the altar of burnt-offering, to build the house of God in Jerusalem. But while the foundation of the new temple was laid, there mingled with the joyful shoutings of the people also the loud wailings of the old men who had seen the former temple in its glory, when they beheld this building undertaken amid circumstances so depressing and sorrowful (Ezra 3:1-13). In addition to this, the Samaritans immediately, when the Jewish rulers refused for conscience sake to permit them to take part with them in the building, sought, by means of influences used at the Persian court, to prevent the carrying on of the building (Ezra 4:1-5). This sad state of matters could not but, at the beginning of the new year, fill the heart of Daniel with deep sorrow, and move him at the return of the time of the passover to mourn in fasting and prayer over the delay of the salvation promised to his people, and to supplicate in behalf of Israel the pardon of their sins, and their deliverance out of the hand of their enemies. Therefore he mourned and fasted before and during the paschal days for three weeks, until on the twenty-fourth day of the month he received a revelation from God.

Was mourning - Because he foresaw the many calamities that would befall the Jews for their sins, especially for destroying the Messiah, and rejecting his gospel.