John Gill Commentary Luke 6:9

"And Jesus said unto them, I ask you, Is it lawful on the sabbath to do good, or to do harm? to save a life, or to destroy it?" — Luke 6:9 (ASV)

Then said Jesus to them
The Scribes and Pharisees, who were watching him, and whose thoughts, and the reasonings of their minds, purposes, and intentions, he full well knew:

I will ask you one thing ;
or question, as they had asked him one before; (Matthew 12:10)

is it lawful on the sabbath days to do good, or to do evil? to
save life, or to destroy it ?
(See Gill on Mark 3:4) to which may be added, that to save life on the sabbath day was agreeable to their own canons: there many things which they allowed might be done on the sabbath day, when life was in danger, which otherwise were not lawful; (See Gill on Matthew 12:8).