Albert Barnes Commentary Psalms 56:10

"In God (I will praise [his] word), In Jehovah (I will praise [his] word)," — Psalms 56:10 (ASV)

In God will I praise his word — Luther renders this, “I will praise the word of God.” The phrase “in God” probably means “in respect to God,” or, “in what pertains to God.” That which he would “particularly” praise or celebrate in respect to God—that which called for the most decided expressions of praise and gratitude—was his “word,” his promise, his revealed truth. So in Psalms 138:2, You have magnified your word above all your name; that is, above all the other manifestations of yourself. The allusion in the passage here is to what God had “spoken” to David, or the “promise” which he had made—the declaration of his gracious purposes in regard to him. Amidst all the perfections of Deity, and all which God had done for him, this now seemed to him to have special preeminence in his praises.

The “word” of God was to him that which impressed his mind most deeply—that which most tenderly affected his heart. There are times when we feel this, and properly feel it; times when, in contemplating the divine perfections and dealings, our minds so rest on his word, on his truth, on what he has revealed, on his gracious promises, on the disclosures of a plan of redemption, on the assurance of a heaven hereafter, and on the instructions which he has given us about himself and his plans—about ourselves, our duty, and our prospects—that this absorbs all our thoughts, and we feel that this is “the” great blessing for which we are to be thankful; this, “the” great mercy for which we are to praise him. What would the life of man be without the Bible! What a dark, gloomy, sad course would ours be on earth if we had nothing to guide us to a better world!

In the Lord will I praise his word — In “Yahweh.” That is, whether I contemplate God by the usual name by which he is known—אלהים 'Elohiym—or by that more sacred name which he has assumed—יהוה Yahweh—that which seems now to me to lay the foundation of loftiest praise and most hearty thanksgiving is that he has spoken to people and made known his will in his revealed truth.