John Gill, on Isa 38:19

The Lord was ready to save me,.... Or, "the Lord to save me (y)"; he was at hand to save him; he was both able and willing to save him; he was a present help in time of need; he arose for his help, and that right early; he very quickly delivered him out of his distress; he, who one day expected death every moment, was the next day in the temple praising God: therefore will we sing my songs; which were made by him, or concerning him, or which he ordered to be sung, as he did the Psalms of David, Ch2 29:30, to the stringed instruments: which were touched with the fingers, or struck with a quill or bow; which distinguishes them from wind instruments, which were blown with the mouth; each of these were used in the temple service: all the days of our life; he had before said "we will sing", meaning his family and his friends with him, his courtiers, princes, and nobles, or he and the singers of Israel; and this he determined to do as long as he and they lived; signifying, that the mercy granted would never be forgotten by him, as well as there would be new mercies every day, which would call for praise and thankfulness: and this he proposed to do in the house of the Lord; in the temple; not only privately, but publicly; not in his closet and family only, but in the congregation of the people; that the goodness of God to him might be more known, and the praise and glory given him be the greater. (y) "Dominus ad servandum me", Montanus; "Jehova est ad salvandum me", Cocceius, Vitringa.