When Peter confessed that Yeshua was the God Man, peter next tried to reprimand Yeshua for saying He muster suffer and die. Yeshua then calls Pete the devil.
Why?
Because the gospel of the kingdom that Pete and co had been sent out to preach (only to jews) was not the gospel of salvation.
Why?
Because the gospel of the kingdom that Pete and co had been sent out to preach (only to jews) was not the gospel of salvation.