Jesus challenged his enemies' belief that God did not allow doing good works on the Sabbath (see Luke 13:10–17).
to save life or to destroy it: This might refer to an incident in which the Maccabees decided to fight if attacked on the Sabbath (1 Maccabees 2:32–41). These great Jewish heroes were willing to kill on the Sabbath day. But the Pharisees did not allow good works on that day. The question Jesus asked embarrassed them. It shamed them into silence, but they still refused to change (Mark 3:5).