John said to him, “Teacher, we saw someone casting out demons in your name, and we tried to stop him, because he was not following us.”  But Jesus said, “Do not stop him, for no one who does a mighty work in my name will be able soon afterward to speak evil of me.  For the one who is not against us is for us.  For truly, I say to you, whoever gives you a cup of water to drink because you belong to Christ will by no means lose his reward.
Temptations to Sin
 “Whoever causes one of these little ones who believe in me to sin, it would be better for him if a great millstone were hung around his neck and he were thrown into the sea.  And if your hand causes you to sin, cut it off. It is better for you to enter life crippled than with two hands to go to hell, to the unquenchable fire.  And if your foot causes you to sin, cut it off. It is better for you to enter life lame than with two feet to be thrown into hell.  And if your eye causes you to sin, tear it out. It is better for you to enter the kingdom of God with one eye than with two eyes to be thrown into hell,  ‘where their worm does not die and the fire is not quenched.’  For everyone will be salted with fire.  Salt is good, but if the salt has lost its saltiness, how will you make it salty again? Have salt in yourselves, and be at peace with one another.”
(Mark 9:38-50 ESV)