P.Berol. 21124 (aka BKT 9.24, TM, Images) is a papyrus that dates to AD 300–399. It is fairly fragmentary and small (not a lot of text, either) so it is difficult to translate in any sort of coherent manner. I’m using Kurt Treu’s transcription as basis for my translation.

Treu, Kurt. “Varia Christiana II.” AfP 32 (1986): 23–24.

P.Berol. 21124 recto, aka BKT 9.24. (from Berliner Papyrusdatenbank)

My translation follows:

Recto

1. […].[…]
2. […] who loosed tḥẹ body aṇḍ tḥẹ[…]
3. […].[.]… to puniṣḥ light from heave[n…]*
4. […]..[.]…. unbroken wall was .[…]*
5. […]the F(ath)er . of us : Adam . having called [up…]
6. […]and[.] . .[.]. the sons of [A]dam : that the f(ath)e[r…]

Verso

1. […] ẉay out : … . […]..[…]
2. […].̣… of the book : And I have found the .[…]
3. […]..[..] summary with ….[…]*
4. […]…. sun (and) the earth: ..[…]

Why is this seen as a hymn of Christ’s descent? The phrase “unbroken wall” in recto line 4 may have some relation with “gates of Hades” in Mt 16:18. That, set with light from heaven being punished, and other discussion of “Adam . having called up” and “the sons of Adam” may point to influence from the Acts of Pilate and Descent of Christ to Hades, a work classified as Christian Apocrypha (or New Testament Apocrypha) that puts forth a traditional view of what may have happened after Christ’s crucifixion that includes scenes in Hades of Old Testament luminaries telling stories about their lives and prophecies/looking forward to Christ’s triumph over death. Des. Hades 3 has Seth (Adam’s son) telling a story, at Adam’s behest, about when Adam died. In this section, there are occurrences of “Father” in close proximity to “Adam” and mention of “sons” and “Adam.”