Anubis anointing Osiris (John baptizing Jesus)
A depiction of Anubis anointing Osiris (Dendera Temple, c.30AD) compared to a portrait of John the baptist baptizing Jesus (600AD), the later being a re-write of the former; both of which deriving the the older model that Ra was reborn each morning, and yearly, out of the water of the Nu (or Nun), aka sun born out of the receding annual 150-day flood of the Nile River.
In religio-mythology, baptism, from the Greek βαπτίζω (baptízō), “I dip in liquid”, refers to immersion of the body or of pouring of water of the head, typically in infant, while certain words are said, done to initiated one into a religion; a ceremonial practice of placing holy water on the head of someone, thereby being symbolic of the sun re-born out of the primordial abyss or Nile River; symbolic of Ra, the sun god, born out Nu (or Nun), the water god.

Overview
The concept of "baptism" is a symbolic ritual associated with or seen as the embodiment of the re-birth of the new sun out of the waters of the Nun or Nile River (Massey, 1906); which is conceptualized, in mirror form, astro-theologically, as a copy of the Aquarius constellation (Bede, 600BC).

Anubis | John the Baptist
The concept of baptism originated in Egypt with the god Anubis who baptized the god Horus (Ѻ)(Ѻ) using the water that ran under the temple, which was considered to be associated with either the god Nun or Osiris, and considered holy. In the Roman recension, Anubis became rescripted as “John the Baptist” and Horus became Jesus.

Quotes
The following are related quotes:

“Hail, thou who dippest thyself [in Nu].”
— Anon (c.1000BC), “Osiris Praise Song” [1]

“In America, the pretext of baptism absolutely extinguished the feelings of humanity.”
Voltaire (1764), Philosophical Dictionary (§:Fanaticism) [6]

“I consider it a degradation and a stain on my honor to submit to baptism in order to qualify myself for state employment in Prussia.”
Heinrich Heine (c.1830), Publication [7]

Plutarch's version of the myth of Isis and Osiris connects the various episodes, many of which can be documented from Egyptian sources, into a single, running narrative (On Isis and Osiris, 12-19). The story begins with Kronos (Geb, the Egyptian earth god) and Rhea (Nut, the Egyptian sky goddess) overcoming the curse of Helios (Re, the sun god) with the help of Hermes (Thoth, the Egyptian moon god) by producing five children on five intercalary days: Osiris, Horus, Typhon (Set), Isis, and Nephthys. As pharaoh of Egypt, Osiris brings civilization to that country and to the whole world. Typhon, however, gathers conspirators and plots to kill Osiris. First, he imprisons Osiris within a coffin and throws it into the Nile River, and later he dismembers the body of Osiris and scatters the pieces all around Egypt. One piece, the penis, is lost forever in the Nile River. In both episodes, the reproductive power of Osiris is sub-merged in the Nile.”
— Marvin Meyer (1999), The Ancient Mysteries [5]

See also
Anoint

References
1. Budge, Wallis. (1904). The Gods of the Egyptians, Volume Two (pg. 260; summer solstice, pg. 264). Dover, 1969.
2. (a) Murdock, Dorothy M. (2008). Christ in Egypt: the Horus-Jesus Connection (§: Who is Anubis?, pgs. 236-). Stellar House Publishing.
(b) Smith, Alexander. (2012). The Holiest Lie Ever (§16: John the Baptist, pgs. 150-). Trafford Publishing.
3. Murdock, Dorothy. (2011). “Was John the Baptist and Egyptian Myth” (Ѻ), Stellar House, Dec 30.
4. Massey, Gerald. (1907), Ancient Egypt, Volume Two (pg. 855). Publisher.
5. Meyer, Marvin. (1999). The Ancient Mysteries: a Sourcebook of Sacred Texts (pg. 160). University of Pennsylvania Press.
6. (a) Voltaire. (1764). Philosophical Dictionary (§:Fanaticism) (txt). Publisher.
(b) Joshi, Sunand T. (2014). The Original Atheists: First Thoughts on Nonbelief (pg. 60). Prometheus Books.
7. Haught, James A. (1996). 2000 Years of Disbelief: Famous People with the Courage to Doubt (pg. 185). Prometheus.

External links
Baptism – Wikipedia.
Baptism of Jesus – Wikipedia.

TDics icon ns