What does it mean when 2 Peter 2:13 says false teachers feast with you?
It means false teachers enter fellowship with church people, even feasting among them, while being spots and blemishes. They appear to share the meal, but they are filled with false teaching and deceit, adulterating God's Word by mixing paganism with biblical truth, and will receive the reward of unrighteousness.
In this section, 2 Peter chapter 2, like Jude, deals with false teachers who will come in the last days. Les teaches that they come from every direction and leave the average believer confused about right and wrong. Peter describes them as receiving the reward of unrighteousness, counting it pleasure to riot in the daytime, spots and blemishes, sporting themselves with their own deceivings while they feast with you. Les explains that this means they come right in and fellowship with church people, yet they are filled with false teaching. Verse 14 adds that they have eyes full of adultery; Scripture often uses adultery for mixing paganism with true biblical truth, adulterating the Word of God. These people are masters at that.
And shall receive the reward of unrighteousness, as they that count it pleasure to riot in the day time. Spots they are and blemishes, sporting themselves with their own deceivings while they feast with you;