Information on Hebrews

A text from the Talmud sets the latest possible date for Hebrews. R. Ishmael died c. 135 CE; if these are his words, the composition of Hebrews (to which Ishmael refers) must have taken place before his death.

R. Zechariah said, in the name of R. Ishmael,
The Holy One – blessed be He – sought to cause the priesthood to go
forth from Shem.
For it is said:
And he was a priest of God Most High. [Gen 14:18]
As soon as he put the blessing of Abraham before the blessing of
God, he caused it to go forth from Abraham, as it is said,
And he blessed him and said:
Blessed be Abraham of God Most High, possessor of
heaven and earth, and blessed be God Most High. [v.19]
Abraham said to him:
Do they put the blessing of the servant before the
blessing of his owner?
Immediately it was given to Abraham, as it is said:
The Lord says to my Lord:
Sit thou at my right hand until I make thy
enemies a footstool for thy feet. [Ps. 110:1]
And further down it is written,
The Lord hath sworn and will not repent,
Thou art a priest forever after the order of
Melchesidek, [v.4] according to the saying of Melchesidek.
And this is what is written.
And he was priest of God Most High. [Gen 14:18]
He was priest; his seed were not priests.

Babylon Talmud, Nedar. 32b, quoted in Travers R. Herford, Christianity in Talmud and Midrash, 1903, I, b, iv; pg 338, item 139.