Jeremiah 20:13

Sing unto the LORD, praise ye the LORD: for he hath delivered the soul of the poor from the hand of evildoers.

Singing to the Lord and praising Him are called for because He rescues the soul of the poor and vulnerable from the hand of evildoers. The praise rests on deliverance, with the poor lifted out of the power of those who do evil. It is the utterance of Jeremiah's faith that God would deliver him personally in the midst of persecution.