Psalms 145:21

My mouth shall speak the praise of the LORD: and let all flesh bless his holy name for ever and ever.

The verse is a personal resolve to use the mouth to speak the praise of the Lord, joined to a call for all flesh — every human being — to bless His holy name for ever and ever. That universal and unending praise is the fitting response to His unsearchable greatness, His mighty and terrible acts declared from one generation to another, the glorious majesty of His honor to be meditated upon, the memory of His great goodness, His righteousness to be sung, and the glory, power, and majesty of His everlasting kingdom and dominion throughout all generations made known to men. All His works praise Him, and His saints praise Him and speak of the glory of His kingdom and His power to make His mighty acts known.

In its immediate setting this praise answers that the Lord is near to all who call upon Him in truth, that He fulfills the desire of those who fear Him, hears their cry and saves them, and preserves all who love Him. Because the deliverance and preservation come from Him, the praise belongs to God and not to human beings.

The verse therefore calls people to awaken to a fuller sense of His mercies and unbounded goodness in order to praise Him.