take somebody's side
pick somebody's side , also: take the side of somebody
choose somebody's side

And you cannot take my side, not so long as we're in their hands.

I find myself more often than not taking the woman's side.

Robert's going to walk over to take his side of things.

He took the left side as Big stood at the right.

If there is only on in ten who'll take your side then we will go.

Never was there a vote in which he did not take the government's side.

She would have thought that he'd take her mother's side.

Wouldn't doing nothing to change the policy also be taking sides?

I certainly could never take sides against one of my parents.

A time comes when a man has to take sides.