John Calvin Commentary Acts 2:28

"Thou madest known unto me the ways of life; Thou shalt make me full of gladness with thy countenance." — Acts 2:28 (ASV)

Thou hast made known. He means that he was restored from death to life by the grace of God. For because he was, as it were, a man raised from death to life, he acknowledges that it was a great and good gift of God. This was fulfilled in Christ in such a way that it lacked nothing for perfection.

As for the members, they have their measure. Therefore Christ was far from corruption, so that he might be the first-fruits of those who rise from death (1 Corinthians 15:23). We shall follow him in our order eventually, but first being turned into dust (1 Corinthians 15:42). What follows, that he was filled with gladness with the countenance of God, agrees with that: Show us thy face, and we shall be safe.

And, again, The light of thy countenance is showed upon us: thou hast put gladness in my heart. For it is only the pleasantness of God’s countenance, which not only makes us glad, but also gives us life; again, when it is turned away, or troubled, we must surely faint.