Isaiah 38:17 - Joseph Benson’s Commentary on the Old and New Testaments

Behold, for peace I had great bitterness “When I perceived and feared no evil, and seemed to enjoy my usual health, then this terrible evil came upon me.” The Hebrew, however, לשׁלום מר לו מר, may be properly rendered, Behold my grievous anguish is turned into ease; or, My great bitterness was unto peace, that is, became the occasion of my safety and comfort, for it drove me to prayer, and prayer prevailed with God for a gracious answer, and the prolonging of my life. Thou hast in love to my soul, &c. That is, in kindness to me, (the soul being put for the man,) delivered it from the pit of corruption This is an emphatical circumstance, for sometimes God prolongs men's days in anger, foreknowing that they will only fill up still more the measure of their iniquities. For thou hast cast all my sins behind thy back Thou hast forgiven those sins that brought this affliction upon me, and, upon that account, hast removed the punishment of them.