John Calvin Commentary Acts 1:24

"And they prayed, and said, Thou, Lord, who knowest the hearts of all men, show of these two the one whom thou hast chosen," — Acts 1:24 (ASV)

In praying, they said. Literally, it is, "Having prayed, they said"; but there is no lack of clarity in the meaning, because his intention was to convey, as follows, that they prayed; and yet he does not recount all the words, being content to briefly show the substance.

Therefore, although they were both of upright conduct, indeed, although they excelled in holiness and other virtues, yet because the integrity of the heart—of which God alone is the knower and judge—is of chief importance, the disciples prayed that God would bring to light what was hidden from men.

The same should be required even today when choosing pastors. For even though we are not to appoint two for one, yet because we may often be deceived, and the discerning of spirits comes from the Lord, we must always pray to God that He will show us which men He intends to be ministers, so that He may direct and govern our decisions.

From this, we may also understand the great importance we must place on integrity and innocence when choosing pastors. Without these, learning, eloquence, and whatever other excellence can be imagined, are as nothing.