The rule is you are both disqualified from the hole.
From the USGA website:
30-3f/6 Player Plays Away from Hole to Assist Partner
Q. In a four-ball competition, a player purposely putts away from the hole to a position slightly farther from the hole than the spot where his partner's ball lies and on the same line to the hole as his partner's ball. The player then putts towards the hole, and the roll of his ball is helpful to his partner in determining how much his putt will break, etc. Is such procedure contrary to the Rules?
A. Such procedure is contrary to the spirit of the game. In match play, in equity (Rule 1-4), the player should be disqualified for the hole and, since his action assisted his partner's play, the partner should incur the same penalty — Rule 30-3f.
In stroke play, the player should incur a penalty of two strokes and, under Rule 31-8, the partner should incur the same penalty.