Contradiction with Matthew 28:20
Matthew 21:17 mentions Jesus departing to Bethany, whereas Matthew 28:20 suggests His continual presence with the disciples.
Matthew 28:20: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, [even] unto the end of the world. Amen.
Contradiction with John 14:18
Matthew 21:17 shows Jesus leaving for Bethany, while John 14:18 promises He will not leave the disciples comfortless.
John 14:18: I will not leave you comfortless: I will come to you. [comfortless: or, orphans]
Contradiction with Hebrews 13:5
Matthew 21:17 describes a temporary departure from Jerusalem, whereas Hebrews 13:5 promises God will never leave or forsake believers.
Hebrews 13:5: [Let your] conversation [be] without covetousness; [and be] content with such things as ye have: for he hath said, I will never leave thee, nor forsake thee.
Contradiction with Matthew 18:20
Matthew 21:17 has Jesus leaving the crowd physically, while Matthew 18:20 speaks of His presence with two or three gathered in His name.
Matthew 18:20: For where two or three are gathered together in my name, there am I in the midst of them.