'Lawful' in the Bible

and certain of the Pharisees said to them, 'Why do ye that which is not lawful to do on the sabbaths?'

how he went into the house of God, and the loaves of the presentation did take, and did eat, and gave also to those with him, which it is not lawful to eat, except only to the priests?'

Then said Jesus unto them, 'I will question you something: Is it lawful on the sabbaths to do good, or to do evil? life to save or to kill?'

and Jesus answering spake to the lawyers and Pharisees, saying, 'Is it lawful on the sabbath-day to heal?'

Is it lawful to us to give tribute to Caesar or not?'