John Calvin Commentary Lamentations 3:58

"O Lord, thou hast pleaded the causes of my soul; thou hast redeemed my life." — Lamentations 3:58 (ASV)

For the same purpose, he now says that God had been his judge to undertake his cause, and not only once, for He had contended for him as though He had been his perpetual advocate. The meaning is that the Prophet (who still speaks in the name of all the faithful) had found God a defender and a helper, not only in one instance but whenever he had been in trouble; for he uses the plural number and says, Thou hast pleaded the pleadings of my soul.

He adds, Thou hast redeemed my life. It is the way of God’s pleading when He delivers us, as it were, from death. Friends do, indeed, sometimes anxiously exert themselves, interposing for our defense, but they do not always succeed. But God is such a pleader of our cause that He is also a deliverer, for our safety is in His hand.