The Epistle of Barnabas is traditionally held to be written by the Barnabas of the New Testament, however, a second option is that it was written by a contemporary of Ignatius and Polycarp name Barnabas of Alexandria. It is a late 1st century or early 2nd century (sometime between 70-132).
Let us further inquire whether the Lord took any care to foreshadow the water|of baptism¦ and the cross. Concerning the water, indeed, it is written, in reference to the Israelites, that they should not receive that baptism which leads to the remission of sins, but should procure another for themselves.
The prophet therefore declares, “Be astonished, O heaven, and let the earth tremble at this, because this people hath committed two great evils: they have forsaken Me, a living fountain, and have hewn out for themselves broken cisterns. Is my holy hill Zion a desolate rock? For ye shall be as the fledglings of a bird, which fly away when the nest is removed.” And again saith the prophet, “I will go before thee and make level the mountains, and will break the brazen gates, and bruise in pieces the iron bars; and I will give thee the secret hidden, invisible treasures, that they may know that I am the Lord God.” And “He shall dwell in a lofty cave of the strong rock.” Furthermore, what saith He in reference to the Son? “His water is sure; ye shall see the King in His glory, and your soul shall meditate on the fear of the Lord.” And again He saith in another prophet, “The man who doeth these things shall be like a tree planted by the courses of waters, which shall yield its fruit in due season; and his leaf shall not fade, and all that he doeth shall prosper. Not so are the ungodly, not so, but even as chaff, which the wind sweeps away from the face of the earth. Therefore the ungodly shall not stand in judgment, nor sinners in the counsel of the just; for the Lord knoweth the way of the righteous, but the way of the ungodly shall perish.”
Mark how He has described at once both the water and the cross. For these words imply, Blessed are they who, placing their trust in the cross, have gone down into the water; for, says He, they shall receive their reward in due time: then He declares, I will recompense them. But now He saith, “Their leaves shall not fade.” This meaneth, that every word which proceedeth out of your mouth in faith and love shall tend to bring conversion and hope to many. Again, another prophet saith, “And the land of Jacob shall be extolled above every land.” This meaneth the vessel of His Spirit, which He shall glorify. Further, what says He? “And there was a river flowing on the right, and from it arose beautiful trees; and whosoever shall eat of them shall live for ever.” This meaneth, that we indeed descend into the water full of sins and defilement, but come up, bearing fruit in our heart, having the fear|of God¦ and trust in Jesus in our spirit. “And whosoever shall eat of these shall live for ever,” This meaneth: Whosoever, He declares, shall hear thee speaking, and believe, shall live for ever. (Brn 11:1-11 APE)