And he called a famine upon the land Here the inspired writer recounts a most illustrious proof of divine providence towards the chosen people, at the time when the covenant might seem to be void and disannulled. The inheritance of the land of Canaan (as has been stated above) was added, as an earnest or pledge for confirmation. The descent of Jacob into Egypt, which deprived his house of the sight of the land, could not make the covenant to perish. In this the constancy of God shone forth the brighter; yea, by this trial he manifested more plainly how provident a father he was in preserving the seed of Abraham. But it is better to consider each particular in the verse. In the first place, it is taught, that the famine which drove Jacob into Egypt did not happen by chance. Although only one particular famine is here treated of, it is to be held as a general principle, that there is no other cause of any scarcity of sustenance except this, that God, in withdrawing his hand, takes away the means of support. The curse of God is expressed more emphatically, when it is said, that the famine was called; as if it were ready at his command, as a minister of his wrath. By this we are instructed, that famine, pestilence, and other scourges of God, do not visit men by chance, but are directed by his hand whither it pleases him, and are obedient to his will. [1] The manner in which the famine was called is next stated, namely, when he brake the staff of bread The metaphor of staff is very appropriate; for God has put into bread the power and property of strengthening man, by a secret virtue which fits it to sustain us. So long as it pleases him to nourish us by such means, a staff as it were lies hidden within it. This staff is broken in two ways; either, first, when he takes away the supply of grain necessary for our nourishment, the sense in which it seems to be used in Ezekiel "Moreover, he said unto me, Son of man, behold, I will break the staff of bread in Jerusalem, and they shall eat bread by weight, and with care; and they shall drink water by measure, and with astonishment;" Ezekiel 4:16 or, secondly, when he breathes in anger upon the bread itself, so that those who would satisfy themselves by devouring it, instead of having their hunger thereby removed, remain famished still. And certainly to the barrenness of the earth this second is commonly added, namely, that he takes away the sustaining power which is in bread; for, as it is declared in Deuteronomy 8:3, bread does not give life of itself, but borrows its secret virtue from the mouth of God.

Footnotes

1 - "Famine is here finely represented as a servant, ready to come and go at the call' and command of God; for calamities, whether public or private, are the messengers of divine justice." -- Horne.

Moreover, he called for a famine upon the land - It was not by chance; not by the mere operation of physical laws, but it was because God "ordered" it. The famine here referred to, as the connection shows, was that which occurred in the time of Jacob, and which was the occasion of the migration into Egypt. There was also a famine in the time of Abraham Genesis 12:10; but the design of the psalmist here is to refer to that period of the Jewish history which pertained to their residence in Egypt, and to the dealings of God with the nation when there, as furnishing an occasion for gratitude. Genesis. 41; 42.
He brake the whole staff of bread - That which supports life, as a staff does a feeble man. See the notes at Isaiah 3:1.

Moreover he called for a famine upon the land: he brake the whole (k) staff of bread.
(k) Either by sending scarcity or the strength and nourishment of it.

Moreover, he called for a famine upon the land,.... On the land of Egypt; or rather on the land of Canaan, where Jacob and his sons sojourned; and which reached to all lands, Genesis 41:56 and calling for it, it came, being a servant at the command of the Lord; see 2-Kings 8:1.
He brake the whole staff of bread; so called, because it is the support of man's life, the principal of his sustenance: as a staff is a support to a feeble person, and which, when broke, ceases to be so. The staff of bread is broken, when either the virtue and efficacy of it for nourishment is taken away or denied; or when there is a scarcity of bread corn; which latter seems to be intended here; see Isaiah 3:1.

God ordered the famine. God
called for a famine--as if it were a servant, ready to come at God's bidding. Compare the centurion's words, as to disease being God's servant (Matthew 8:8-9).
upon the land--namely, Canaan (Genesis 41:54).
staff of bread--what supports life (Leviticus 26:26; Psalm 104:15; Isaiah 3:1).

"To call up a famine" is also a prose expression in 2-Kings 8:1. To break the staff of bread (i.e., the staff which bread is to man) is a very old metaphor, Leviticus 26:26. That the selling of Joseph was, providentially regarded, a "sending before," he himself says in Genesis 45:5. Psalm 102:24 throws light upon the meaning of ענּה ב. The Kerמ רגלו is just as much without any occasion to justify it as עינו in Ecclesiastes 4:8 (for עיניו). The statement that iron came upon his soul is intended to say that he had to endure in iron fetters sufferings that threatened his life. Most expositors take בּרזל as equivalent to בּבּרזל, but Hitzig rightly takes נפשׁו as an object, following the Targum; for ברזל as a name of an iron fetter
(Note: Also in ancient Arabic firzil (after the Aramaic פרזלא) directly signifies an iron fetter (and the large smith's shears for cutting the iron), whence the verb. denom. Arab. farzala, c. acc. pers., to put any one into iron chains. Iron is called בּרזל from בּרז, to pierce, like the Arabic ḥdı̂d, as being the material of which pointed tools are made.)
can change its gender, as do, e.g., צפון as a name of the north wind, and כבוד as a name of the soul. The imprisonment (so harsh at the commencement) lasted over ten years, until at last Joseph's word cam to pass, viz., the word concerning this exaltation which had been revealed to him in dreams (Genesis 42:9). According to Psalm 107:20, דברו appears to be the word of Jahve, but then one would expect from Psalm 105:19 a more parallel turn of expression. What is meant is Joseph's open-hearted word concerning his visions, and אמרת ה is the revelation of God conveying His promises, which came to him in the same form, which had to try, to prove, and to purify him (צרף as in Psalm 17:3, and frequently), inasmuch as he was not to be raised to honour without having in a state of deep abasement proved a faithfulness that wavered not, and a confidence that knew no despair. The divine "word" is conceived of as a living effectual power, as in Psalm 119:50. The representation of the exaltation begins, according to Genesis 41:14, with שׁלח־מלך
(Note: Here שׁלח is united by Makkeph with the following word, to which it hurries on, whereas in Psalm 105:28 it has its own accent, a circumstance to which the Masora has directed attention in the apophthegm: שׁלוחי דמלכא זריזין שׁלוחי דחשׁוכא מתינין (the emissaries of the king are in haste, those of darkness are tardy); vid., Baer, Thorath Emeth, p. 22.)
and follows Genesis 41:39-41, Genesis 41:44, very closely as to the rest, according to which בּנפשׁו is a collateral definition to לאסּר (with an orthophonic Dag.) in the sense of בּרצונו: by his soul, i.e., by virtue of his will (vid., Psychology, S. 202; tr. p. 239). In consequence of this exaltation of Joseph, Jacob-Israel came then into Egypt, and sojourned there as in a protecting house of shelter (concerning גּוּר, vid., supra, p. 414). Egypt is called (Psalm 105:23, Psalm 105:27) the land of Chaam, as in Psalm 78:51; according to Plutarch, in the vernacular the black land, from the dark ashy grey colouring which the deposited mud of the Nile gives to the ground. There Israel became a powerful, numerous people (Exodus 1:7; Deuteronomy 26:5), greater than their oppressors.

Staff of bread - Bread, which is the staff or support of our lives.