Albert Barnes Commentary Psalms 59:16

"But I will sing of thy strength; Yea, I will sing aloud of thy lovingkindness in the morning: For thou hast been my high tower, And a refuge in the day of my distress." — Psalms 59:16 (ASV)

But I will sing of thy power — That is, I will praise you for the manifestation of your power in rescuing me from danger.

Yea, I will sing aloud of thy mercy in the morning — When the light dawns; when these troubles are over; when the night of calamity will have passed by. There is an allusion here, probably, to the fact that they surrounded the place where he lived at night (Psalms 59:6; Psalms 59:14); but there is also the implied idea that that night was emblematic of sorrow and distress. The morning would come; a morning after such a night of sorrow and trouble; a morning of joy and gladness, when he would feel that he had complete deliverance. Then he would praise God aloud. Compare the notes at Isaiah 21:12.

For thou hast been my defense and refuge in the day of my trouble — That is, he looked to the time when he would feel this; when looking back he could say this; when in view of it he would praise God.