I have called upon thee, etc. This verb being put in the past tense denotes a continued act; and, therefore, it includes the present time. The Hebrew word ky, ki, which we translate surely, often signifies because, and if it is so understood in this passage, the meaning will be, that David took encouragement to pray, because, depending upon the promise of God, he hoped that his prayers would not be in vain. But, perhaps, it may be thought preferable to change the tense of the verb as some do, so as to give this meaning, I will pray, because I have hitherto experienced that thou hast heard [1] my prayers. I have, however, chosen the exposition what appears to me the more simple. David, in my judgment, here encourages and animates himself to call upon God, from the confident hope of being heard, as if he had said, Since I call upon thee, surely, O God, thou wilt not despise my prayers. Immediately after he beseeches God to bestow upon him the blessings of which he told us he entertained an assured hope.

Footnotes

1 - The Septuagint renders the verb in the past tense, "Epekousas mou," "Thou hast heard me." The Syriac and Vulgate give a similar rendering. The verb, in the Hebrew, is in the future; but it is a common thing in Hebrew to use the future tense for the past.

I have called upon thee for thou wilt hear me, O God - The meaning of this is, "I have called on thee heretofore, and will do it still, because I am certain that thou wilt hear me." That is, he was encouraged to call upon God by the conviction that he would hear his prayer, and would grant his request. In other words, he came to God in faith; in the full belief of his readiness to answer prayer, and to bestow needed blessings. Compare John 11:42; Hebrews 11:6.
Incline thine ear unto me - See the notes at Psalm 17:1.
My speech - My prayer. The reference here, as in Psalm 17:1, is to prayer "uttered" before God; and not mere mental prayer.

Incline thine ear unto me - David prayed from a conviction that God would hear: but he could not be satisfied unless he received an answer. In a believer's mind the petition and the answer should not be separated.

I have called upon thee, (f) for thou wilt hear me, O God: incline thine ear unto me, [and hear] my speech.
(f) He was assured that God would not refuse his request.

I have called upon thee,.... In prayer. This had been the constant practice of the psalmist, and he still continued in it;
for thou wilt hear me, O God; God is a God hearing prayer; he is used to hear his people, and they have frequent experience of it, and they may be assured that whatsoever they ask according to his will, and in the name of Christ, he will hear; and such an assurance is a reason engaging the saints to a constant calling upon God, Psalm 116:2; and such confidence of being always heard Christ had, John 11:41;
incline thine ear unto me, and hear my speech; meaning his prayer, which he now directed to him in full assurance of being heard, and is as follows.

wilt hear me--that is, graciously (Psalm 3:4).

It is only now, after his inward parts and his walk have been laid open to Jahve, that he resumes his petition, which is so well justified and so soundly based, and enters into detail. The אני
(Note: The word is pointed אני, in correct texts, as אני always is when it has Munach and Dech follows, e.g., also Psalm 116:16. This Gaja demands an emphatic intonation of the secondary word in its relation to the principal word (which here is קראתיך).)
found beside קראתיך (the perfect referring to that which has just now been put into execution) is meant to imply: such an one as he has described himself to be according to the testimony of his conscience, may call upon God, for God hears such and will therefore also hear him. הט אזנך exactly corresponds to the Latin au-di (aus-cul-ta). The Hiph. הפלה (הפליא, Psalm 31:22, cf. Psalm 4:4) signifies here to work in an extraordinary and marvellous manner. The danger of him who thus prays is great, but the mercies of God, who is ready and able to help, are still greater. Oh that He may, then, exhibit all its fulness on his behalf. The form of the address resembles the Greek, which is so fond of participles. If it is translated as Luther translates it: "Show Thy marvellous lovingkindness, Thou Saviour of those who trust in Thee, Against those who so set themselves against Thy right hand," then חוסים is used just as absolutely as in Proverbs 14:32, and the right hand of God is conceived of as that which arranges and makes firm. But "to rebel against God's right (not statuta, but desteram)" is a strange expression. There are still two other constructions from which to choose, viz., "Thou Deliverer of those seeking protection from adversaries, with Thy right hand" (Hitz.), or: "Thou Helper of those seeking protection from adversaries, at Thy right hand" (Aben-Ezra, Tremell.). This last rendering is to be preferred to the two others. Since, on the one hand, one says מחסה מן, refuge from..., and on the other, חסה בּ to hide one's self in any one, or in any place, this determining of the verbal notion by the preposition (on this, see above on Psalm 2:12) must be possible in both directions. ממּתקוממים is equivalent to ממתקוממיהם Job 27:7; and חוסים בימינך, those seeking protection at the strong hand of Jahve. The force of the ב is just the same as in connection with הסתּתּר, 1-Samuel 23:19. In Damascus and throughout Syria - Wetzstein observes on this passage - the weak make use of these words when they surrender themselves to the strong: Arab. anâ b-qabḍt ydk, "I am in the grasp of thy hand (in thy closed hand) i.e., I give myself up entirely to thee."
(Note: Cognate in meaning to חסה ב are Arab. 'sttr b and tadarrâ b, e.g., Arab. tḏrrâ b-'l-ḥâ'ṭ mn 'l-rı̂ḥ he shelters (hides) himself by the wall from the wind, or Arab. bâl‛ḍât mn 'l-brd, by a fire against the cold, and Arab. ‛âḏ, which is often applied in like manner to God's protection. Thus, e.g., (according to Bochri's Sunna) a woman, whom Muhammed wanted to seize, cried out: Arab. a‛ûḏu b-'llh mnk, I place myself under God's protection against thee, and he replied: Arab. ‛uḏti bi-ma‛âḏin, thou hast taken refuge in an (inaccessible) asylum (cf. Job, i. 310 n. and ii. 22 n. 2).)