Contradiction with Luke 24:49
Jesus instructs the disciples to wait in Jerusalem until they are empowered with the Holy Spirit, contradicting the immediate sending out in Mark 6:7.
Luke 24:49: And, behold, I send the promise of my Father upon you: but tarry ye in the city of Jerusalem, until ye be endued with power from on high.
Contradiction with Matthew 28:19-20
Jesus commands making disciples of all nations, whereas Mark 6:7 focuses on a specific mission to the twelve.
Matthew 28:19-20: Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: [teach...: or, make disciples, or, Christians of all nations]
Contradiction with Acts 1:4-5
The disciples are told to wait in Jerusalem for the promise of the Father, contrasting the active mission in Mark 6:7.
Acts 1:4-5: And, being assembled together with [them], commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, [saith he], ye have heard of me. [being...: or, eating together]
Contradiction with Matthew 10:5-6
Jesus instructs not to go to the Gentiles or Samaritans, while Mark 6:7 sends the disciples out without such restriction.
Matthew 10:5-6: These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into [any] city of the Samaritans enter ye not:
Contradiction with John 20:21-22
Jesus sends the disciples with a different context and empowers them with the Holy Spirit, whereas Mark 6:7 involves giving authority over unclean spirits.
John 20:21-22: Then said Jesus to them again, Peace [be] unto you: as [my] Father hath sent me, even so send I you.
Contradiction with Luke 9:3
The instructions given by Jesus about taking nothing for the journey contrast with Mark 6:7's focus on authority and sending out.
Luke 9:3: And he said unto them, Take nothing for [your] journey, neither staves, nor scrip, neither bread, neither money; neither have two coats apiece.