Acts 1:3

Irenaeus Against Heresies Book I

The other eighteen Aeons are made manifest in this way: that the Lord, [according to them,] conversed with His disciples for eighteen months[35]

Irenaeus Against Heresies Book IV

For thus it was that the Lord discoursed with, the disciples after His resurrection from the dead, proving to them from the Scriptures themselves "that Christ must suffer, and enter into His glory, and that remission of sins should be preached in His name throughout all the world."[360]

Tertullian On Baptism

wherein, too, the resurrection of the Lord was repeatedly proved[199]

Origen Against Celsus Book II

But it is recorded in the Acts, that "being seen during forty days," He expounded to His disciples "the things pertaining to the kingdom of God."[155]

Constitutions of the Holy Apostles Book V

We who have eaten and drunk with Him, and have been spectators of His wonder fill works, and of His life, and of His conduct, and of His words, and of His sufferings, and of His death, and of His resurrection from the dead, and who associated with Him forty days after His resurrection,[63]