The Prophet intimates in this verse that we cannot stand firm in adversities, except we be content with God alone and his favor; for as soon as we depart from him, any adversity that may happen to us will cause our faith to fail. It is then the only true foundation of patience and hope to trust in God alone; and this is the case when we are persuaded that his favor is sufficient for our perfect safety. In this sense it is that David calls God his portion. (Psalm 16:5.) But there is in the words an implied contrast, for most men seek their happiness apart from God. All desire to be happy, but as the thoughts of men wander here and there, there is nothing more difficult than so to fix all our hopes in God so as to disregard all other things. This then is the doctrine which the Prophet now handles, when he says, that those alone could hope, that is, persevere in hope and patience, who have so received God as their portion as to be satisfied with him alone, and to seek nothing else besides him. But he speaks emphatically, that his soul had thus said. Even the unbelieving are ashamed to deny what we have stated, that the whole of our salvation and happiness is found in God alone. Then the unbelieving also confess that God is the fountain of all blessings, and that they ought to acquiesce in him; but with the mouth only they confess this, while they believe nothing less. This then is the reason why the Prophet ascribes what he says to his soul, as though he had said, that lie did not boast, like hypocrites, that God was his portion, but that of this lie had a thorough conviction. My soul has said, that is, I am fully convinced that God is my portion; therefore will I hope in him. We now understand the meaning of this passage. It remains for us to make an application of this doctrine. That we may not then fail in adversities, let us bear in mind this truth, that all our thoughts will ever wander and go astray, until we are fully persuaded that God alone is sufficient for us, so that lie may become alone our heritage. For all who are not satisfied with God alone, are immediately seized with impatience, whenever famine oppresses them, or sword threatens them, or any other grievous calamity. And for this reason Paul also says, "If God be for us, who can be against us? I am persuaded that neither famine, nor nakedness, nor sword, nor death, nor life, can separate me from the love of God, which is in Christ." (Romans 8:31, 35-39.) Then Paul lays hold of the paternal favor of God as a ground of solid confidence; for the words in Christ sufficiently show that those are mistaken interpreters who take this love passively, as though he had said, that the faithful would never cease to love God, though he exercised them with many afflictions. But Paul meant that the faithful ought so to fix their minds on God alone, that whatever might happen, they would not yet cease to glory in him. Why? because God is their life in death, their light in darkness, their rest in war and tumult, their abundance in penury and want. It is in the same sense our Prophet now says, when lie intimates that none hope in God but those who build on his paternal favor alone, so that they seek nothing else but to have him propitious to them. It afterwards follows, --

The Lord is my portion - "My portion is Yahweh," see Numbers 18:20; Psalm 16:5 ff.
Therefore will I hope in him - A more full expression of the confidence present in the prophet's mind in Lamentations 3:21, but based now upon God's faithfulness in showing mercy.

The Lord is my portion - See on Psalm 119:67 (note).

The LORD [is] my (l) portion, saith my soul; therefore will I hope in him.
(l) The godly put their whole confidence in God, and therefore look for no other inheritance, as (Psalm 16:5).

The Lord is my portion, saith my soul,.... The prophet, or the church, whom he represents, rises and increases in the exercise of faith; from considering the mercies, compassions, and faithfulness of God, concludes a sure and firm interest in him, as a portion and inheritance. The Lord is the portion of his people in life and in death, in time and to eternity; all he is, and has, is theirs; they are heirs of him, and shall enjoy him for ever, and therefore shall not be consumed; he is a portion large and full, inexpressibly rich and great, a soul satisfying one, and will last for ever. And happy are those, who from their hearts, and with their souls, under a testimony of the Spirit of God to their spirits, and through a gracious experience of him, can say he is their portion and exceeding great reward, as the church here did; and these may say with her, as follows:
therefore will I hope in him: for deliverance from all evils and enemies; for present supplies of grace; and for the enjoyment of future glory and happiness.

(Numbers 18:20; Psalm 16:5; Psalm 73:26; Psalm 119:57; Jeremiah 10:16). To have God for our portion is the one only foundation of hope.