Do you ever buy food for unsaved people? It can speak volumes to a hardened sinner. We are told in Scripture, "For this is the will of God, that by doing good you may put to silence the ignorance of foolish men."( 1 Peter 2:15) So, if you find that someone is always arguing with you, put him to silence by buying something delicious for him. Then leave it where he will find it, along with a tasteful card. Don't write anything "religious" on the card. Simply say, "I saw this and thought that you might like it." Don't give him anything to argue with. Then pray that your small expression of love will soften his hard heart, so that you can speak to him about the big expression of love revealed in the cross. Don't put this off for another day. It may never come. There goes another minute. Gone forever. Go share your faith while you still have time.