I will praise thee, O Lord - That is, in view of the merciful interpositions referred to in the psalm Psalms 9:3-5, and in view of the attributes of God’s character which had been displayed on that occasion Psalms 9:7-12.
With my whole heart - Not with divided affection, or with partial gratitude. He meant that all his powers should be employed in this service; that he would give utterance to his feelings of gratitude and adoration in the loftiest and purest manner possible.
I will show forth - I will recount or narrate - to wit, in this song of praise.
All thy marvelous works - All his works or doings fitted to excite admiration or wonder. The reference here is particularly to what God had done which had given occasion to this psalm, but still the psalmist designs undoubtedly to connect with this the purpose to give a general expression of praise in view of all that God had done that was fitted to excite such feelings.