Rosh Hashannah Reflection: The ritual of Christian baptism as reported in Acts was (mostly) familiar to the period Jewish audience

So, I have been working through an in-depth commentary on the book of Acts as I have been learning and copying Acts in Latin. This passage on Pentecost and Baptism is particularly relevant right now during Rosh Hashannah 2021 (the Hebrew "New Year" preceding the Day of Atonement) as baptism, vis, ritual immersion in water as a symbol of atonement, was particularly practiced during the New Year, not inconceivably by Jesus of Nazareth Himself. It is, of course, recorded that he underwent baptism by John the Baptizer. John practiced and particulary emphasized atonement-by-immersion but hardly invented the practice.

My copy of the commentary, "El Libro de Hechos" por F.F. Bruce is in Spanish. "The Book of Acts" by F.F. Bruce is also available in English, I just don't happen to have it (nor have I the foggiest idea whether page numbers match), so I'll copy the relevant short bits of Spanish here and provide my own translation. Any mistakes are my own, almost certainly not that of F. F. Bruce. The  passage refers to Acts 2:38-41, the events immediately following the outpouring of the Holy Spirit on the day of Pentecost (an existing Old Testament Holy Day). Given here in English:

BSB  ³⁸ Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.
³⁹ This promise belongs to you and to your children and to all who are far off, to all whom the Lord our God will call to Himself.”
⁴⁰ With many other words he testified, and he urged them, “Be saved from this corrupt generation.”
⁴¹ Those who embraced his message were baptized, and about three thousand were added to the believers that day.

Bruce's commentary text for v. 38:

Como en la predicación de Juan, la llamada al bautismo está unida a la llamada al arrepentimiento. Aparentemente el mandamiento de ser bautizados no ocasionó sorpresa. La práctica del bautismo resultaba bastante familiar a la audiencia de Pedro, a quien (como los oyentes de Juan antes que ellos) se les requería recibir el bautismo en agua como señal externa y visible de su arrepentimiento. Pero ahora había dos características nuevas en el rito del bautismo con agua: es la administración “en el nombre del Jesucristo” y se asoció con “el don del Espíritu Santo”. Esta nueva característica enfatiza, en las palabras de G.W.H. Lampe, que el bautismo cristiano “es todavía un rito escatológico, porque apuntaba hacia la redención final, la cual está aún por venir en el regreso en gloria del Señor; pero, considerado en relación a Juan el bautista, representaba la realización y cumplimiento de la esperanza de Israel”

And my rough English:

As in the preaching of Juan, the call to baptism is joined to the call to repentence. Apparently the command to be baptized occasioned no surprise [from the Jews there assembled]. The practice of baptism, it followed, was already familiar to Peter's audience, who (as with John's listeners before them) were called upon to receive the baptism in water as a visible and external sign of their repentance. But now he [Peter] required two new characteristics in the rite of baptism in water: it is administered in the "name of Jesus Christ" and associated with "the gift of the Holy Spirit". This new characteristic is emphasized, in the words of G.W.H. Lampe, that the Christian baptism "is in whole form an escatological [that is, of or concerning the end of days] rite, because it aimed to make that surrender final which is yet to come in the glorious return of the Lord, but, when considered in relation to John the Baptizer, represents the completion of the hope of Israel." [internal citation omitted]

--- Pasaje de: "El libro de los Hechos" por F. F. Bruce. Scribd. https://www.scribd.com/book/350613212 pp 161

As the commentary goes on to describe, both the existing (pre-Christian) ritual of baptism in water and the "gift of the Holy Sprit" whose outpouring that this (Jewish) assembly had just witnessed, are tied inextricably to the honest determination to repent and turn back to YHWH. Second Temple Jews immersing themselves (particularly but not exclusively) on Rosh Hashannah prior to Yom Kippur's communal Day of Atonement did not differ in that respect. Elsewhere, archaeologists have noted that the existence of basins for ritual immersion in water can practically be used to map the post-Diaspora spread of the remnants of Israel and Judea in ancient times.

The accounting imagery (not expressly anchored in scripture but an explanatory doctrine, likely never intended to be taken literally) of the between-time after sundown on Rosh Hashannah and before sundown on Yom Kippur is that YHWH, having closed the books on the previous year is writing his budget for the next, deciding who will be blessed and cursed, who will be written in the Book of Life and who will-- not. "On Rosh Hashannah it is writren; on Yom Kippur it is sealed." This in turn is obliquely, perhaps confusingly, referred to in Christian doctrine regarding the "Book of the Lamb" or "Book of Life of the Lamb" (e.g. Revelation 13:8). To a contemporaneous audience familiar with Rosh Hashannah and its oral tradition, the reference may have been much less opaque. But the expression here is similar to what G.W.H. Lampe is quoted as saying with respect to the essential eschatology of Christian baptism: that it is a poor bargain to endlessly petition to be left in the Book of Life for merely one more year (which many of us scarcely earn) against the chance of being written into the Book of the Lamb as an inheritor of the imminent and eternal Kingdom of the annointed Messiah (which not a single one of us has earned or ever will).

That all being said, the traditional ritual of periodic immersion in water as an external and visible sign of repentence is not without its use, nor is the yearly recognition of the Appointed Times for atonement. To the contrary, we can all of us use every reminder we can get. As linear creatures, we need timely reminders of our nature and duties. These were gifts to fallible forgetful humans intended to help us recognize and walk the steep path we are meant to daily walk. With the gift of the Holy Spirit and the constant help of divine grace, the impossible path becomes possible (though seldom easy). Thus the words of the Aveinu, "Our Father", itself a summary of Hebrew tradition:

Lead us not into temptation,

Yet free us from evil.

Min-hara (מן-הרע) in Hebrew, from (the) evil (one), is a reminder of min-hahar (מן-ההר), from the mountain, merely one letter off, referring to the traditional imagery of the steep path and constant struggle for right action. Sometimes-- no matter the tradition we come from-- we need to stop and wash off the dirt of the mountain to see the image of the divine within.