John Calvin 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. In the original, the pronoun is not expressed, but we are to infer from the parallel verse that preceded it that it is understood. The repetition adds emphasis to the sentiment, intimating that even though God delayed the perceptible manifestation of His favor, and might seem to deal harshly by abandoning him to the word (essentially giving him nothing more), he was resolved to glory in it with undiminished confidence.

When, in such a spirit, we honor the word of God, though deprived of any present experience of His goodness or His power, we set to our seal that God is true (John 3:33). The repetition amounts to an expression of his determination that, despite all circumstances that might appear to contradict the promise, he would trust in it and persist in praising it, both now, from now on, and forever.

How desirable it is that the Lord’s people generally would accustom themselves to think in the same manner, and find in the word of God a reason for never-failing praise amidst their worst trials! They may encounter many mercies calling for thanksgiving, but they can hardly have taken one step in life before they will feel the necessity of reliance on the bare promise.

A similar reason may be given for his repetition of the sentiment in the 11th verse—In God have I hoped, etc. We will find people universally agreed in the opinion that God is an all-sufficient protector, but observation proves how ready we are to distrust Him under the slightest temptation. When exposed to the opposition of assailants formidable in strength, strategy, or any worldly advantages, let us learn with David to set God in opposition to them, and we will quickly be able to view the mightiest of them without dismay.