Albert Barnes Commentary Psalms 147:7

"Sing unto Jehovah with thanksgiving; Sing praises upon the harp unto our God," — Psalms 147:7 (ASV)

Sing unto the Lord with thanksgiving - Accompany the praise of God - the expression of worship - with a grateful remembrance of the past. The one will aid the other, and the two will constitute acceptable and proper worship. The first word here means properly to answer, or respond; and the idea would seem to be, that we are to make a suitable response or answer to the manifold blessings which we have received at the hand of God.

Sing praise upon the harp unto our God - On the word harp, see the notes at (Isaiah 5:12). The harp was an instrument commonly employed in divine worship. See the notes at (Psalms 33:2): “Praise the Lord with harp.” Compare (Psalms 43:4); (Psalms 49:4); (Psalms 57:8); (Psalms 71:22).