'Lawful' in the Bible

But some of the Pharisees said to them, Why do ye what is not lawful to do on the sabbath?

how he entered into the house of God and took the shewbread and ate, and gave to those also who were with him, which it is not lawful that any eat, unless the priests alone?

Jesus therefore said to them, I will ask you if it is lawful on the sabbath to do good, or to do evil? to save life, or to destroy it?

And Jesus answering spoke unto the doctors of the law and Pharisees, saying, Is it lawful to heal on the sabbath?

Is it lawful for us to give tribute to Caesar, or not?