Galatians 2:20 "I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me." Luke 14:27 "And whoever does not bear his cross and come after Me cannot be My disciple." Matthew 10:38 "And he who does not take his cross and follow after Me is not worthy of Me." Matthew 16:24 "Then Jesus said to His disciples, "If anyone desires to come after Me, let him deny himself, and take up his cross, and follow Me." Galatians 6:14 "But God forbid that I should boast except in the cross of our Lord Jesus Christ, by whom the world has been crucified to me, and I to the world."
LUTHER: “Whoever is no crucianus, if I may so express it, is also no christianus. That is to say, he who does not bear the cross is no Christian; he is not like his Master Christ.”
(St. L. II:467, cited in Pieper's Christian Dogmatics, III:70.)