Albert Barnes Commentary Acts 1:3

"To whom he also showed himself alive after his passion by many proofs, appearing unto them by the space of forty days, and speaking the things concerning the kingdom of God:" — Acts 1:3 (ASV)

He showed himself. The resurrection of Jesus was the great fact on which the truth of the gospel was to be established. Therefore, the sacred writers so often refer to it and establish it by so many arguments. Since that truth lay at the foundation of all that Luke was about to record in his history, it was important that he clearly state the sum of its evidence at the beginning of his work.

After his passion. After he suffered, referring particularly to his death, as the consummation of his sufferings. The word passion, in common usage, typically means excitement or agitation of mind, such as love, hope, fear, anger, etc. In the original, the word means to suffer. The word passion, applied to the Savior, denotes his last sufferings. Thus, in the Litany of the Episcopal Church, it is beautifully said, "By your agony and bloody sweat; by your cross and passion, good Lord, deliver us." The Greek word of the same derivation is rendered sufferings in 1 Peter 1:11; 1 Peter 4:13; Colossians 1:24.

By many infallible proofs. The word rendered here as infallible proofs does not occur elsewhere in the New Testament.

In Greek authors, it denotes an infallible sign or argument by which anything can be certainly known—Schleusner.

Here it means the same: evidence that he was alive which could not deceive, or about which they could not be mistaken. That evidence consisted in his eating with them, conversing with them, meeting them at various times and places, working miracles (John 21:6–7), and uniformly showing himself to be the same Friend with whom they had been familiar for more than three years. This evidence was infallible for the following reasons:

1. Because it was unexpected by them. They had clearly not believed that he would rise again (John 20:25; Luke 24). There was therefore no delusion resulting from any expectation of seeing him, or from a design to impose on men.
2. It was impossible that they could have been deceived in relation to one with whom they had been familiar for more than three years. No one could be imposed upon and made to believe that they really saw, talked with, and ate with a friend whom they had known so long and familiarly, unless it was real.
3. There were enough of them to avoid the possibility of deception. Though it might be pretended that one man could be imposed on, yet it could not be that an imposition could be practiced for forty days on eleven men, who were all at first incredulous.
4. He was with them sufficient time to give evidence. It might be pretended, if they had seen him but once, that they were deceived. But they saw him often, and for the space of more than a month,
5. They saw him in various places and times where there could be no deception. If they had pretended that they saw him rise, or saw him at twilight in the morning when he rose, it might have been said that they were deluded by some remarkable appearance. Or it might have been said that, expecting to see him rise, their hopes and agitations would have deceived them, and they would easily have fancied that they saw him. But it is not pretended by the sacred writers that they saw him rise. An impostor would have affirmed this and would not have omitted it. But the sacred writers affirmed that they saw him after he had risen; when they were free from agitation; when they could judge coolly: in Jerusalem; in their company when at worship; when journeying to Emmaus; when in Galilee; when he went with them to Mount Olivet; and when he ascended to heaven.
6. He appeared to them as he had always done: as a friend, companion, and benefactor. He ate with them, performed a miracle before them, was engaged in the same work as he was before he suffered, renewed the same promise of the Holy Spirit, and gave them his commands respecting the work which he had died to establish and promote. In all these circumstances, it was impossible that they should be deceived.

Being seen by them forty days. There are no less than thirteen different appearances of Jesus to his disciples recorded. For an account of them, see Barnes' commentary on Matthew 28:20.

Speaking to them, etc. He was not only seen by them, but he continued the same topics of discourse as before his sufferings, thus showing that he was the same person that had suffered and that his heart was still intent on the same great work. Our Savior's heart was filled with the same design in his life and death, and when he rose, thus showing us that we should aim at the same great work in all the circumstances of our being. Afflictions, persecutions, and death never turned him from this great plan, nor should they be allowed to divert our minds from the great work of redemption.

The things pertaining to the kingdom of God. For an explanation of this phrase, "the kingdom of God," see Barnes' commentary on Matthew 3:2.

The meaning is, Jesus gave them instructions about the organization, spread, and edification of his church.