For he supposed - This is not mentioned by Moses; but it is not at all improbable. When they saw him “alone” contending with the Egyptian; when it was understood that he had come and taken vengeance on one of their oppressors, it might have been presumed that he regarded himself as directed by God to interpose, and save the people.
Related Commentaries of Acts 7:25
Acts 7:25
25 Fora he supposed his brethren would have understood how that God by his hand would deliver them: but they understood not.