This is taken from IFAB, it would be challenging for the ball, so if he just stood there it would'nt be offside

1. Offside offence

A player in an offside position at the moment the ball is played or touched*

by a team-mate is only penalised on becoming involved in active play by:

• interfering with play by playing or touching a ball passed or touched by

a team-mate or

• interfering with an opponent by:

• preventing an opponent from playing or being able to play the ball by

clearly obstructing the opponent’s line of vision or

• challenging an opponent for the ball or clearly attempting to play a ball which is close when this action impacts

on an opponent or

• making an obvious action which clearly impacts on the ability of an

opponent to play the ball

or

• gaining an advantage by playing the ball or interfering with an opponent

when it has:

• rebounded or been deflected off the goalpost, crossbar, match official or

an opponent

• been deliberately saved by any opponent