Psalm 149:1 - Sing His praise in the congregation of saints

Praise the LORD. Sing to the LORD a new song, his praise in the assembly of the saints.

Praise ye the LORD. Sing unto the LORD a new song, and his praise in the congregation of saints.

The call for a new song comes at several points in the Psalms (33:3; 40:3; 144:9). These words encourage more than just novelty; they call for freshness and integrity in performing music.

One of the primary emphases in the Book of Psalms is that the praise of God is to take place in the center of the worshiping community. Praise unites the people of God (33:1-3).

Radmacher, E. D., Allen, R. B., & House, H. W. (1999). Nelson's new illustrated Bible commentary (Ps 149:1). Nashville: T. Nelson Publishers.

Psalm 66:18-19 - If I had cherished sin in my heart...

If I had cherished sin in my heart, the Lord would not have listened; but God has surely listened and heard my voice in prayer

If I regard iniquity in my heart, the Lord will not hear me: But verily God hath heard me; he hath attended to the voice of my prayer.

Ongoing sin in a believer's life hinders effective prayer (Ps. 32). This is especially true if we cherish certain unconfessed sins in our lives.

Proverbs 23:17 says "Do not let your heart envy sinners, but always be zealous for the fear of the LORD."

We are commanded not to cherish sin or envy sinners.