As mentioned above the early Diatessaron mentioned the Jordan stopping its flow, This concept was shared by other early writers. The river also was thought to have momentarily reversed course.
The Testimony of Truth describes the scene:
But the Son of Man came forth from Imperishability, being alien to defilement. He came to the world by the Jordan river, and immediately the Jordan turned back. And John bore witness to the descent of Jesus.
This text is one of many that understood the scene and its symbolism as metaphor for transition, but that is another topic.
Orthodox Christians to this day celebrate the Epiphany in part by singing a hymn called, En Iorthani Vaptizomenou Sou Kyrie (When you Were Baptized in the Jordan Lord) and dropping crosses into the Jordan. Many believe the waters momentarily reverse. The Jordan Reversed Its Flow! / OrthoChristian.Com
The obvious source of this tradition (like many if not all) is the OT. Specifically, the original Jesus (Joshua) and the crossing of the Jordan.
Hippolytus quoting a Naassene work:
This, according to them, is the spiritual generation. This, he says, is the great Jordan which, flowing on (here) below, and preventing the children of Israel from departing out of Egypt–I mean from terrestrial intercourse, for Egypt is with them the body,–Jesus drove back, and made it flow upwards.(RoAH book 5)
In this quote Jesus is the OT character who was typologically understood.