From a Christmas Day sermon by Martin Luther

He who confidently believes Christ has accomplished these things (i.e., His substitiutionary life and death, and His resurrection from the dead, for that person) immediately, in the twinkling of an eye, possesses salvation.

All his sins and the reality of death and hell are removed. Nothing more than such faith is necessary to salvation.

--Luther's Second Church Postil for Christmas Day (Titus 3:4-8)