First Reading: Acts 1:15–17, 21–26
15In those days Peter stood up among the believers (together the crowd numbered about one hundred twenty persons) and said, 16Friends, the scripture had to be fulfilled, which the Holy Spirit through David foretold concerning Judas, who became a guide for those who arrested Jesus — 17for he was numbered among us and was allotted his share in this ministry." 21So one of the men who have accompanied us during all the time that the Lord Jesus went in and out among us, 22beginning from the baptism of John until the day when he was taken up from us — one of these must become a witness with us to his resurrection." 23So they proposed two, Joseph called Barsabbas, who was also known as Justus, and Matthias. 24Then they prayed and said, "Lord, you know everyone's heart. Show us which one of these two you have chosen 25to take the place in this ministry and apostleship from which Judas turned aside to go to his own place." 26And they cast lots for them, and the lot fell on Matthias; and he was added to the eleven apostles.
Happy are they who have not walked in the counsel of
nor lingered in the way of sinners,
nor sat in the seats of the scornful!
Their delight is in the law of the LORD,
and they meditate on his law day and night.
They are like trees planted by streams of water,
bearing fruit in due season, with leaves that do not wither;
everything they do shall prosper.
It is not so with the wicked;
they are like chaff which the wind blows away.
Therefore the wicked shall not stand upright when judgment comes,
nor the sinner in the council of the righteous.
For the LORD knows the way of the righteous,
but the way of the wicked is doomed.
Second Reading: 1 John 5:9–13
9If we receive human testimony, the testimony of God is greater; for this is the testimony of God that he has testified to his Son. 10Those who believe in the Son of God have the testimony in their hearts. Those who do not believe in God have made him a liar by not believing in the testimony that God has given concerning his Son. 11And this is the testimony: God gave us eternal life, and this life is in his Son. 12Whoever has the Son has life; whoever does not have the Son of God does not have life.
13I write these things to you who believe in the name of the Son of God, so that you may know that you have eternal life.
Gospel: John 17:6–19
6I have made your name known to those whom you gave me from the world. They were yours, and you gave them to me, and they have kept your word. 7Now they know that everything you have given me is from you; 8for the words that you gave to me I have given to them, and they have received them and know in truth that I came from you; and they have believed that you sent me. 9I am asking on their behalf; I am not asking on behalf of the world, but on behalf of those whom you gave me, because they are yours. 10All mine are yours, and yours are mine; and I have been glorified in them. 11And now I am no longer in the world, but they are in the world, and I am coming to you. Holy Father, protect them in your name that you have given me, so that they may be one, as we are one. 12While I was with them, I protected them in your name that you have given me. I guarded them, and not one of them was lost except the one destined to be lost, so that the scripture might be fulfilled. 13But now I am coming to you, and I speak these things in the world so that they may have my joy made complete in themselves. 14I have given them your word, and the world has hated them because they do not belong to the world, just as I do not belong to the world. 15I am not asking you to take them out of the world, but I ask you to protect them from the evil one. 16They do not belong to the world, just as I do not belong to the world. 17Sanctify them in the truth; your word is truth. 18As you have sent me into the world, so I have sent them into the world. 19And for their sakes I sanctify myself, so that they also may be sanctified in truth.