"O Lord, I have heard thy speech, and was afraid: O Lord, revive thy work in the midst of the years, in the midst of the years make known; in wrath remember mercy." ~Habakkuk 3:2
"We now apprehend the real meaning of the Prophet. After having confessed that the Israelites justly trembled at God's voice, as they saw themselves deservedly given up to perdition, he then appeals to the mercy of God, and prays God to revive His own work. He brings forward here nothing but the favour of adoption: thus he confesses that there was no reason why God should forgive His people, except that He had been pleased freely to adopt them and to choose them as His peculiar people; for on this account it is that God is wont to show His favour towards us even to the last. As, then, this people had been once chosen by God, the Prophet records this adoption, and prays God to continue and to fulfil to the end what He had begun. With regard to the half course of life, the comparison ought to be observed; for we see that the race of Abraham was not chosen for a short time, but until Christ the Redeemer was manifested. Now we have this in common with the ancient people, that God adopts us, that He may at length bring us into the inheritance of eternal life. Until, then, the work of our salvation is completed, we are, as it were, running our course. We may therefore adopt this form of prayer, which is prescribed for us by the Holy Spirit,- that God would not forsake His own work in the middle of our course."
"When he now subjoins - in wrath remember mercy, is intended to anticipate an objection; for this thought might have ocurred to the faithful- "there is no ground for us to hope pardon from God, whom we have so grievously provoked, nor is there any reason for us to rely any more on the covenant which we have perfidiously violated." The Prophet meets this objection, and he flees to the gracious favor of God, however much he percieved that the people would have to suffer the just punishment of their sins, such as they deserved. He then confesses that God was justly angry with His people, and yet that the hope of salvation was not on that account closed up, for the Lord had promised to be propitious. Since God then is not inexorable towards His people - nay, while He chastises them He ceases not to be a father; hence the Prophet connects here the mercy of God with His wrath."
"We have elsewhere said that the word wrath is not to be taken according to its strict sense, when the faithful or elect are spoken of; for God does not chastise them because He hates them; nay, on the contrary, He thereby manifest the care He has for their salvation. Hence the scourges by which God chastises His children are testimonies of His love. But the Scripture represents the judgement with which God visits His people as wrath, not towards their persons but towards their sins. Though then God shows love to His chosen, yet He testifies when He punishes their sins that iniquity is hated by Him. When God then comes forth as it were as a judge, and shows that sins displease Him, He is said to be angry with the faithful; and there is also in this a reference to the perceptions of men; for we cannot, when God chastises us, do otherwise than feel the accusations of our own conscience. Hence then is this hatred; for when our conscience condems us we must necessarily acknowledge God to be angry with us, that is with respect to us. When therefore we provoke God's wrath by our sins we feel Him to be angry with us; but yet the Prophet connects together things which seem wholly contrary- even that God would remember mercy in wrath; that is, that He would show Himself displeased with them in such a way as to afford to the faithful at the same time some taste of His favour and mercy by finding Him to be proptitous to them."
"We now then perceive how the Prophet had joined his last clause to the foregoing. Whenever, then, the judgement of the flesh would lead us to despair, let us ever set up against it this truth - that God is in such a way angry that He never forgets His mercy - that is, in His dealings with His elect." ~ John Calvin