But the Son of Man goes around eating and drinking, and you say, “That man eats and drinks too much! He is even a friend of tax collectors and sinners.” Yet Wisdom is shown to be right by what it does.
As Jesus was leaving, he saw a tax collector named Matthew sitting at the place for paying taxes. Jesus said to him, “Come with me.” Matthew got up and went with him.
Later, Jesus and his disciples were having dinner at Levi's house. Many tax collectors and other sinners had become followers of Jesus, and they were also guests at the dinner.
If an unbeliever invites you to dinner, and you want to go, then go. Eat whatever you are served. Don't cause a problem for someone's conscience by asking where the food came from.