100:1-5 An exhortation to praise God, and rejoice in him. - This song of praise should be considered as a prophecy, and even used as a prayer, for the coming of that time when all people shall know that the Lord he is God, and shall become his worshippers, and the sheep of his pasture. Great encouragement is given us, in worshipping God, to do it cheerfully. If, when we strayed like wandering sheep, he has brought us again to his fold, we have indeed abundant cause to bless his name. The matter of praise, and the motives to it, are very important. Know ye what God is in himself, and what he is to you. Know it; consider and apply it, then you will be more close and constant, more inward and serious, in his worship. The covenant of grace set down in the Scriptures of the Old and New Testament, with so many rich promises, to strengthen the faith of every weak believer, makes the matter of God's praise and of his people's joys so sure, that how sad soever our spirits may be when we look to ourselves, yet we shall have reason to praise the Lord when we look to his goodness and mercy, and to what he has said in his word for our comfort.

5. The reason: God's eternal mercy and truth (Ps 25:8; 89:7).