In verses 13 and 14 the psalmist charges the priests to praise Jehovah in His executing of judgment for His people and in His repenting concerning His servants for the sake of His name, which is His memorial throughout all generations.
Verses 19 and 20 are the charge to the house of Israel, the house of Aaron, and the house of Levi, all of whom feared Jehovah, to bless Jehovah. To bless God is to speak well of Him. Every psalm is a blessing to God because every psalm is a well-speaking concerning God.
Verse 21 is a word about blessing Jehovah from Zion, who dwells in Jerusalem. This is the conclusion of this charge given to the priests by a common person who was close to God and concerned for His interests.
The subject of Psalm 136 is the charging of the people to give thanks to Jehovah for His everlasting lovingkindness. Many of the details in this psalm are similar to the details in Psalm 135.
Verse 1 speaks of giving thanks to Jehovah for His being good.
Verses 2 through 4 are a charge to give thanks to the God of gods and the Lord of lords, to Him who alone does great and wondrous deeds.