After leaving Egypt, Moses and his gang went on a lot of wacky adventures. At some point Moses took it upon himself to try his hand at mountain climbing. When he got to the top of Mount Sinai he received the Decalogue, as well as some other words of wisdom. But from whom did he receive the law? The bible gives us two answers from which to choose.
First, in Exodus 19:20, god summons Moses to the top of the mountain. Skip to verse 20:22 and we see that god tells Moses to tell the Israelites that he received the law directly from god.
But when Paul recounted this story to the Galatians, we get a different answer. In verse 3:19 Paul says that Moses (as the “mediator”) was given the law by angels.
This is a striking contradiction because Galatians is a book of the New Testament. Paul should’ve had a copy of Exodus at his fingertips. He could’ve easily cross-referenced his own work with the Old Testament, but for whatever reason he didn’t.
The Atheist Papers 
I would speculate that the confusion stems from the use of Hebrew אלהים (Elohim) instead of YAHWEH at the beginning of the Ten Commandments. Elohim frequently refers to angels, gods, and anybody who exhibits powers, even humans kings, and judges. I would not expect Paul to err, but later translation could definitely confuse the word Elohim for angels. Notice that angels are mentioned nowhere in all interactions between Moses and YHWH.