Charles Ellicott Commentary Psalms 138:8

"Jehovah will perfect that which concerneth me: Thy lovingkindness, O Jehovah, [endureth] for ever; Forsake not the works of thine own hands." — Psalms 138:8 (ASV)

Perfect that which concerneth me. — Or, as in the analogous phrase (Psalms 57:2), will complete for me — that is, either “all my undertakings,” or, as in Philippians 1:6, “what he has begun in and for me.”

Forsake not. — Better, the works of Thine hands; do not leave them unfinished. (See for the same verb Nehemiah 6:3; Proverbs 4:13: let her not go.)

The special intention of the prayer depends on the origin of the psalm. If it arose out of the troubles of rebuilding Jerusalem and reconstituting the state, it is intelligible and expressive. Or the reference may be to all Jehovah’s gracious intentions for Israel.