This Bible contradiction is from the Skeptic's Annotated Bible.
Verses
Those who are not with Jesus are against him.
Matthew 12:30 View context
“Whoever is not with me is against me, and whoever does not gather with me scatters.
Luke 11:23 View context
“Whoever is not with me is against me, and whoever does not gather with me scatters.
Those who are not against Jesus are for him.
Mark 9:40 View context
for whoever is not against us is for us.
Note: This puts those who are indifferent or undecided in the “for him” category in the first instance and in the “against him” category in the second instance.
Luke 9:50 View context
“Do not stop him,” Jesus said, “for whoever is not against you is for you.”