John Wesley on Exodus 32:27

Slay every man his brother - That is, Slay all those that you know to have been active for the making and worshipping of the golden calf, though they were your nearest relations or dearest friends. Yet it should seem they were to slay those only whom they found abroad in the street of the camp; for it might be hoped that those who were retired into their tents were ashamed of what they had done.