Why did Peter command the beggar to walk in the name of Jesus Christ of Nazareth?

Answer 1

Jesus brings the healing of the beggar, Peter doesn't.Jesus works through him, and Peter makes this known that it is in Jesus's name, not his that a miracle is performed.

Maybe Peter did the healing, or maybe it was Jesus through Peter.

Answer 2

In Acts of the Apostles, there is a subtle comparison between the apostles Peter and Paul, with similar miracles performed or experienced or performed by each, but such that Peter is always seen as the more worthy apostle. In this case, Peter's first miraculous cure, he calls on the name of Jesus and the faithful saw the healed beggar praising God, providing the opportunity for some outstanding proselytising. Paul’s first cure was remarkably similar, involving another man lame since birth. Paul's miracle was clumsy and without apparent purpose, given that Paul did not tell the man about Jesus and he was even mistaken for a pagan god.

Having Peter loudly command the beggar in the name of Jesus and having Paul's miracle performed with no mention of Jesus, is part of that comparison.