Albert Barnes Commentary Lamentations 3:40-42

"Let us search and try our ways, and turn again to Jehovah. Let us lift up our heart with our hands unto God in the heavens. We have transgressed and have rebelled; thou hast not pardoned." — Lamentations 3:40-42 (ASV)

The prophet urges men to search out their faults and amend them (Lamentations 3:40).

And turn again to the Lord—or, “and return to Yahweh.” The preposition (to) in the Hebrew implies not halfway, but the whole.

Literally, Let us lift up our heart unto our hands unto God in heaven; (Lamentations 3:41) as if the heart first lifted up the hands, and then with them mounted up in prayer to God. In real prayer, the outward expression is caused by the emotion stirring within.