"By what power or by what name did you do this?"
A badly crippled man had been healed by the apostles Peter and John. The difference could be seen by everyone in the temple in Jerusalem because the healed man went about walking and leaping and praising God! Everyone was happy — except the religious leaders who were furious, and probably jealous.
Peter and John were put in prison overnight. Next day they were asked in court, "By what power or by what name did you do this?" (v7) They replied that the man's healing was all due to the risen Jesus Christ, and, they added, "...there is salvation in no one else, for there is no other name under heaven... by which we must be saved." (Acts 4:12) The powerful name of Jesus!
Our salvation depends on that powerful name of Jesus. It is only Jesus who saves sinners. But the name of Jesus is also a disturbing name. The religious leaders of the time hated the name of Jesus Christ. Many people still do, because Jesus convicts them of their sin and they prefer their sin to following Christ. But those who do follow him find that the powerful name of Jesus gives them the courage to tell others about their Saviour and what he can do for them. That powerful name is still working miracles in our world today.
Lord Jesus Christ, help me to witness in the power of your name to tell those who need to hear your saving words. Amen.