Bite the hand that feeds you
Definition 1 of 1
Pro Tip 1/3Use With Caution
This phrase often has a negative connotation, implying ingratitude or disloyalty. 
He criticized his mentor publicly, truly biting the hand that feeds him.
Pro Tip 2/3Metaphorical Meaning
Understand that it's a metaphor about damaging relationships with a benefactor. 
By leaking company secrets, she's biting the hand that feeds her.
Pro Tip 3/3Non-Literal
Remember, 'biting' and 'feeding' are not physical here but represent actions and support. 
Talking back to his supporters, he didn't realize he was biting the hand that feeds him.