The Holy Spirit lays hold of a person's will and works in him the new birth and conversion...

Dr. Luther has written that a person's will in his conversion is purely passive, that is, that it does nothing at all.  This is to be understood with respect to divine grace in the kindling of the new movements, that is, when God's Spirit, through the heard Word or the use of the holy Sacraments, lays hold of a person's will and works in him the new birth and conversion.  When the Holy Spirit has worked and accomplish this, and a person's will has been changed and renewed by His divine power and working alone, then the new will of that person is an instrument and organ of God the Holy Spirit.  So that person not only accepts grace, but he cooperates with the Holy Spirit in the works that follow.

~BOC, FE, II, 18