The question is not about whether the miracle happened, but where these two fishermen received the authority to do it. The charge was vague, but not Peter's answer. Accusing the court is a bold move inspired by the Holy Spirit. They have rejected the Cornerstone or Capstone that God sent to build His Kingdom. Jesus had quoted this same verse within their earshot a few months before and they responded with anger.
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Peter and John , being from Galilee, had not been educated in their Rabbinical schools. However, the Council knew enough about Jesus to recognize his character and teachings in these men. This healed defense witness was irrefutable, just as the empty tomb was indisputable. For we cannot deny that a significant miracle was performed by them, and everybody living in Jerusalem knows it. They could neither deny it nor explain it.