Psalms 135:20

Bless the LORD, O house of Levi: ye that fear the LORD, bless the LORD.

The summons to bless the Lord is addressed to the house of Levi. That same summons is extended to all who fear the Lord, calling each of them to bless him. The verse stands within a group of devotional psalms. Those psalms are largely praise to Jehovah because his loving-kindness and tender mercy endure forever.