Claim. Because John the Baptist’s doubts undermined the foundation of faith he had laid, Jesus had to lower himself to John’s position and fast forty days in the wilderness to restore the foundation of faith for the second worldwide course — paralleling how Moses had to redo the foundation of faith via a forty-year Midian exile after the first national course failed.
Elaboration. dp-3-the-providence-of-restoration-under-the-leadership-of-jesus §3.2.1 names the structural mechanism: when john-the-baptist sent disciples asking “Are you he who is to come, or shall we look for another?” (Matt 11:3) and denied being Elijah (21), he undermined his testimony and led the Jewish people to disbelieve jesus. The foundation of faith JtB had laid was thereby invaded by Satan.
The repair mechanism: Jesus, “though he came as God’s only begotten Son and the Lord of Glory” and “was not meant to walk a path of suffering,” took on JtB’s mission. The forty-day fast was not a personal devotional discipline but a dispensation of forty for the separation of Satan performed from the position of John the Baptist. This is why Jesus “enjoined Peter not to reveal to the Jewish people that he was the Messiah” — he was operating in JtB’s role, not yet in the messianic role, for the purpose of this phase.
The parallel to Moses: when the first national course aborted at the Egyptian-killing, Moses fled to Midian for forty years to restore the foundation of faith for the second course. Jesus’s forty-day fast achieves the same structural function at the worldwide scope, compressed in time-scale because Jesus operates substantially while Moses operated as image. The structural lesson: when a forerunner fails, the principal must descend to the forerunner’s position and pay analogous indemnity before resuming his own mission.