Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
This chapter is evidently connected with the subject treated of in the thirty-sixth. Baruch, who had written the prophecies of Jeremiah, and read them publicly in the temple, and afterwards to many of the princes, is in great affliction because of the awful judgments with which the land of Judah was about to be visited; and also on account of the imminent danger to which his own life was exposed, in publishing such unwelcome tidings, Jer 45:1-3. To remove Baruch's fear with respect to this latter circumstance, the prophet assures him that though the total destruction of Judea was determined because of the great wickedness of the inhabitants, yet his life should be preserved amidst the general desolation, Jer 45:4, Jer 45:5.
The word that Jeremiah - spake unto Baruch - This is another instance of shameless transposition. This discourse was delivered in the fourth year of Jehoiakim, several years before Jerusalem was taken by the Chaldeans. It is a simple appendage to chap. 36, and there it should have been inserted.
Thou didst say, Wo is me now! - All that were the enemies of Jeremiah became his enemies too; and he needed these promises of support.
The Lord hath added grief to my sorrow - He had mourned for the desolations that were coming on his country, and now he mourns for the dangers to which he feels his own life exposed; for we find, from Jer 36:26, that the king had given commandment to take both Baruch and Jeremiah, in order that they might be put to death at the instance of his nobles.
Behold, that which I have built - I most certainly will fulfill all those threatenings contained in the roll thou hast written; for I will destroy this whole land.
And seekest thou great things for thyself? - Nothing better can be expected of this people: thy hopes in reference to them are vain. Expect no national amendment, till national judgments have taken place. And as for any benefit to thyself, think it sufficient that God has determined to preserve thy life amidst all these dangers.
But thy life will I give unto thee for a prey - This is a proverbial expression. We have met with it before, Jer 21:9, Jer 38:2, Jer 39:18; and it appears to have this meaning. As a prey or spoil is that which is gained from a vanquished enemy, so it is preserved with pleasure as the proof and reward of a man's own valor. So Baruch's life should be doubly precious unto him, not only on account of the dangers through which God had caused him to pass safely, but also on account of those services he had been enabled to render, the consolations he had received, and the continual and very evident interposition of God in his behalf. All these would be dearer to him than the spoils of a vanquished foe to the hero who had overcome in battle.
Spoil may signify unlooked-for gain. The preservation of his life, in such circumstances, must be more than he could reasonably expect; but his life should be safe, and he should have it as a spoil, whithersoever he should go. This assurance must have quieted all his fears.