Note 4 at 1 Cor. 4:13: Paul's use of the phrases "filth of the world" and "offscouring of all things" alludes to certain heathen customs of Paul's day. These were the words used to refer to certain human sacrifices.

The Greeks would choose the most worthless person available and maintain them for one year at public expense, in effect, fattening them for the kill. Then with great circumstance, they would offer them as a sacrifice to the gods and say, "be thou our propitiation."

Paul is saying that this is the way the Corinthians had viewed him. They had forgotten that Paul is the one the Lord used to introduce them to Christ (v. 15).