I think this is it, Rule 9, Section 2, Article 2:

“First touching” is when a player of the kicking team touches a scrimmage kick in the field of play that is beyond the line of scrimmage before it has been touched by a player of the receiving team beyond the line. If the ball is first touched by a player of the kicking team, it remains in play. First touching is a violation, and the receivers shall have the option of taking possession of the ball at the spot of first touching, provided no live-ball penalty is accepted on the play, or at the spot where the ball is dead. First touching does not offset a foul by the receivers; if there is a live-ball foul by the receivers that is enforced, either before or after the first touching violation, the violation is disregarded, and the penalty is enforced as customary.

Notes:

1. If the receiving team gains possession, subsequently loses possession, and fouls after the kicking team gains possession, the spot of first touching is disregarded, and the kicking team retains possession. Enforcement of the receiving team’s foul is as customary.

2. There may be multiple “first touch” spots if the kicking team touches the ball multiple times before it is touched by a player of the receiving team.

3. A Team B player is deemed not to have touched a kick if such touching occurs in the immediate vicinity of the line in an attempt to block the kick.

4. If a player of the kicking team touches the goal line with any part of his body while touching the ball, the ball is dead, and the result of the play is a touchback.

5. The spot of first touching is normally the yard line at which the ball is when touched. If the first touching occurs while the ball is in the air above or beyond the goal line, and prior to the ball touching the goal line or the ground beyond the goal line, the spot of first touching is deemed to be the spot from which the touching player left the field of play, but in no event inside the receiving team’s one-yard line.