Charles Ellicott Commentary Psalms 59:9

"[Because of] his strength I will give heed unto thee; For God is my high tower." — Psalms 59:9 (ASV)

His strength. —This gives no intelligible meaning, and Psalm 59:17 shows that the ancient versions (and some manuscripts) are right in reading my strength (vocative). The first two words of the next verse must also be brought back to this: My strength, on You let me wait. For God is my fortress, God of my grace (or mercy), i.e., my gracious or merciful God.