A 2×4 wood stud in a dwelling measures 1 1/2″ x 3 1/2″. What is the largest hole that may be bored through the center of the wide face of this stud for installation of unprotected non-metallic sheathed cable and still meet the requirements of the NEC?

A 2×4 wood stud in a dwelling measures 1 1/2″ x 3 1/2″. What is the largest hole that may be bored through the center of the wide face of this stud for installation of unprotected non-metallic sheathed cable and still meet the requirements of the NEC?