The Baptism in the Jordan
The Baptism by John of Jesus in the Jordan is widely accepted by scholars as an historically accurate event. It either took place, it is believed, at Bethabera in Perea, or Enon near Salim. Rivers can be - and still are - used for Mikvehs - the water for ritual immersion has to be either rainwater or running water such as in a river. Men also went to the Mikveh, to be cleansed of ritual impurity such as that contracted by contact with a corpse. Many Orthodox men today will go to the Mikveh every Friday, before Shabbat, so they will be both physically and spiritually clean before the Sabbath. One must bathe, including washing one's hair, before entering the Mikveh. Any parts of the body "covered" by dirt are not considered to have come into contact with the "living" water of the Mikveh, thus nullifying the purification.
Baptism (a Greek word meaning 'washing') is a form of ritual washing that is a continuation of the ritual cleansing laid down in the Torah. The Torah required washing for a variety of reasons and occasions. Washing of utensils, the washing of the body, and the washing in a Mikvah after women had their period are all part of ancient Jewish life, and in many cases, modern Jewish life. One of these ritual washings were for those who wanted to convert to Judaism, marking the end of one life and the beginning of another with the washing away of the old life and renewal in the new.
Throughout his life, John sought to turn Jews from their old life which had become distant from God and to bring them through repentance to a renewed relationship with God. Jesus did the same. He continually sought to bring people back to God, from whom they had strayed. But to understand the significance of the baptism, which Orthodoxy sees as the start of Jesus ministry, one needs to look 200 years beforehand.
At that time there were three main strands which influenced Jewish thinking, and, of course, the thinking and experiences behind the ministries of both John and Jesus. The Pharisees (the ancestors of today's Judaism), the Sadducees (the Temple priesthood) and the Essenes (meaning 'pious ones'). The Essenes were probably an offshoot of the Pharisaical school, but took a rather rigid adherence to the Law to bring them closer to God. The Sadducees, who disappeared around AD 70 after the destruction of the Temple, didn't believe in an afterlife, while Essenes and Pharisees did. While the Essenes and the Pharisees were focused on the letter of the Law, Jesus wanted to bring people awake to the spirit of the Law.
One branch of the Essenes organised themselves into fraternities, praying together, worshipping together in their homes, and eating communal meals together. Some scholars have suggested that Jesus, when he gathered the apostles and disciples into His own fraternity, was influenced by this example, and that as a result the early church had very similar beliefs in certain respects. Other scholars have seen John the Baptist in a similar light.