A Little Leaven

Galatians 5:8-10 NASB
8 This persuasion did not come from Him who calls you.
9 A little leaven leavens the whole lump of dough.
10 I have confidence in you in the Lord, that you will adopt no other view; but the one who is disturbing you shall bear his judgment, whoever he is.

How does Paul know that this hindrance to the Galatians obeying the truth does not come from Him who calls you? Who is Him who calls you?
Let's begin with the last question. In Galatians 1:6, Paul referred to "Him who called you." He mentions his own calling in Galatians 1:15. Who is "Him who called and calls you"?
Romans 8:28 is the first footnote in my Bible for verse 8. If you read it, you will see why Paul knows without a doubt that the One who calls us did not cause this hindrance.
So, does Paul know who's responsible for causing this hindrance?
What does he say is going to happen to the responsible party?
What did he say about this responsible party in Galatians 1:8-9?
What does Paul say happens when a little leaven gets into the dough?
What is he talking about? Let's look at the footnote for this verse--1 Corinthians 5:6. Read it.
From reading that verse, does it seem as if leavening the whole lump is a good or bad thing?
Read the next verses--1 Corinthians 5:7-8.
What did Paul tell the Corinthians to do?
Is there any old leaven in your life that needs to be cleaned out?