A.T. Robertson Commentary Acts 4:7

"And when they had set them in the midst, they inquired, By what power, or in what name, have ye done this?" — Acts 4:7 (ASV)

In the midst (εν τω μεσω). The Sanhedrin sat in a semicircle.

They inquired (επυνθανοντο). Imperfect middle, began to inquire.

Or in what name (η εν ποιω ονοματ). As if by some magical formula such as exorcists practised (Acts 19:13) as if to catch them by (Deuteronomy 13:1).

Have ye done this (εποιησατε τουτο υμεις). Note emphatic use of υμεις (ye).