John Calvin Commentary Luke 24:19

"And he said unto them, What things? And they said unto him, The things concerning Jesus the Nazarene, who was a prophet mighty in deed and word before God and all the people:" — Luke 24:19 (ASV)

Powerful in deed and in word. Luke has used nearly the same form of expression concerning Stephen, (Acts 7:22) where he says of Moses, by way of commendation, that he was powerful in words and in actions. But in this passage it is uncertain if it is on account of miracles that Christ is said to be powerful in actions (as if it had been said that he was endowed with divine virtues that proved he was sent from heaven), or if the phrase is more extensive, and means that he excelled both in ability to teach and in holiness of life and other remarkable endowments. I prefer the latter of these views.

Before God and all the people. The addition of these words should not be considered superfluous, for they mean that the high excellence of Christ was so well known, and was demonstrated by such undoubted proofs, that he had no hypocrisy or vain ostentation. And from this we may obtain a brief definition of a true Prophet, namely, that to what he speaks he will also add power in actions, and will not only strive to appear excellent before men, but to act with sincerity as under the eyes of God.