When I heard, my belly trembled; my lips quivered at the voice: rottenness entered into my bones, and I trembled in myself, that I might rest in the day of trouble: when he cometh up unto the people, he will invade them with his troops.
When I heard, my belly trembled - namely, at the judgments which God had declared (Habakkuk 1:1-17) were to be inflicted on Judea by the Chaldeans.
Belly - the bowels were thought by the Hebrews to be the seat of yearning compassion (Jeremiah 31:20 "My bowels are troubled for him") Or, "heard" may refer to Habakkuk 3:3, "O, Lord, I have heard thy speech, and was afraid." 'When I heard as to Yahweh's coming interposition for Israel against the Chaldeans, being still at some distance' (Habakkuk 2:3): so also in the next clause, "the voice" (Maurer). I prefer understanding the cause of Habakkuk's trembling on hearing, to be the whole series of judgments, beginning with those coming on Judea by the Chaldeans, and then about to descend on the Chaldeans themselves from God, to which in this chapter immediate reference is made (Habakkuk 3:3-15).
At the voice - of the divine threatenings (Habakkuk 1:6). The faithful tremble at the voice alone of God, before He inflicts punishment. Habakkuk speaks in the person of all the faithful in Israel.
And I trembled in myself - i:e., I trembled all over (Grotius).
That I might rest in the day of trouble. The true and only path to rest is through such fear. Whoever is securely torpid and hardened toward God will be tumultuously agitated in the day of affliction, and so will bring on himself a worse destruction; but he who in time meets God's wrath, and trembles at His threats, prepares the best rest for himself in the day of affliction (Calvin). Henderson translates, 'yet I shall have rest.' Habakkuk thus consoling his mind. Though trembling at the calamity coming, yet I shall have rest in God (Isaiah 26:3). But that sentiment does not seem to be directly asserted until Habakkuk 3:17-18, as the words following at the close of this verse imply.
When he cometh up unto the people, he will invade them - rather (as the English version is a mere truism), connected with the preceding clause, 'that I might rest, etc., when he (the Chaldean foe) cometh up unto the people (the Jews), that he may cut them off' (Calvin). The Hebrew х yªguwdenuw (H1464), from gaadad (H1413), or guwd (H1464), to congregate: and gªduwd (H1416), a troop or band] for "invade" means, to rush upon, or to attack and cut off with congregated troops.