John Calvin Commentary Psalms 31:24

"Be strong, and let your heart take courage, All ye that hope in Jehovah." — Psalms 31:24 (ASV)

Be of good courage. This exhortation is to be understood in the same way as the previous one. For the steadfastness which the Psalmist here urges is founded on the love of God about which he had spoken, when, renouncing all the enticements of the world, we embrace with our whole hearts the defense and protection which he promises to us.

His exhortation to courage and firmness is indeed necessary, because when anyone begins to rely on God, he must expect and arm himself to endure many assaults from Satan.

1. First, we are to calmly commit ourselves to the protection and guardianship of God, and strive for the experience of his goodness to pervade our whole minds.
2. Secondly, thus equipped with steady firmness and unfailing strength, we are to stand prepared to endure new conflicts every day. However, since no one is able on his own to endure these conflicts, David urges us to hope for and ask for the spirit of fortitude from God—a point especially worthy of our attention.

For this teaches us that when the Spirit of God reminds us of our duty, he does not examine what each man’s ability is, nor does he measure men’s service by their own strength, but rather stimulates us to pray and implore God to correct our defects, as he alone can do this.