"John the Baptist’s ministry grew in popularity, as recounted in Matthew 3:5–6: "People went out to him from Jerusalem and all Judea and the whole region of the Jordan. Confessing their sins, they were baptized by him in the Jordan River." To be baptized by John was to admit your sin and repent of it—which was, of course, a great way to be prepared for the Savior’s coming. The repentance associated with John’s baptism also kept the self-righteous out of the water, as they did not see themselves as sinners."
https://www.gotquestions.org/life-John-Baptist.html
"Mandaeans are an ethnic and religious group who revere John the Baptist, along with other Biblical figures including Adam and Noah."
https://theworld.org/stories/2016-10-06/these-iraqi-immigrants-worship-john-baptist-theyre-not-christians
"Thought to have originated 2,000 years ago in Mesopotamia — modern day Iraq and Iran — the Mandaean community reveres John the Baptist, who they call Yehyea Yahana, and water's purifying force.
Baptism, or masbuta, is the key ritual of this gnostic faith"
https://www.abc.net.au/news/2017-07-21/meet-the-mandaeans-sydneys-followers-of-john-the-baptist/8727720
"11Verily I say unto you, Among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he. 12And from the days of John the Baptist until now the kingdom of heaven suffereth violence, and the violent take it by force."
https://biblehub.com/kjv/matthew/11.htm
"9And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan."
https://biblehub.com/kjv/mark/1.htm
"12That seeing they may see, and not perceive; and hearing they may hear, and not understand; lest at any time they should be converted, and their sins should be forgiven them."
https://biblehub.com/kjv/mark/4.htm
"40He hath blinded their eyes, and hardened their heart; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them."
https://biblehub.com/kjv/john/12.htm
"The Pharisee said to me, This Nazarene has deceived you badly, filled your ears with lies, closed your minds, and turned you from the traditions of your parents.
When I, John, heard this, I turned away from the temple and went to a mountainous and barren place. I was distressed within, and I said,
How was the savior selected?
Why was he sent into the world by his father?
Who is his father who sent him?"
http://www.gnosis.org/naghamm/apocjn-meyer.html