Separate the wheat from the chaff

Means very much the same thing as separate the sheep from the goats and, moreover, is from the same source - the Bible. It is implicit in Jeremiah 23:28, “What is the chaff to the wheat? Saith the Lord.” Also, in Matthew 3:12, “He will thoroughly purge his floor, and gather his wheat into the garner; but he will burn up the chaff with unquenchable fire.”