Psalm 21
Psalm 21:1–13 looks forward to the day when God’s King will finally destroy all of God’s enemies. In times of persecution it is an encouragement to remember that the Day of Judgment will come where all wrongs will be righted. This might be a good song to sing after your sermon.
Psalm 42
Psalm 42:1–11 is a song of lament. The believer feels far from God and he is mocked by those around him for his faith. Speaking to himself, he says that he will yet praise the Lord. He will keep trusting God even in times of hardship and pain.
17 But the high priest rose up, and all who were with him (that is, the party of the Sadducees), and filled with jealousy