Charles Ellicott Commentary Matthew 12:30

"He that is not with me is against me, and he that gathereth not with me scattereth." — Matthew 12:30 (ASV)

He that is not with me is against me — At first, these words seem to conflict with the answer given to the sons of Zebedee. They had reported seeing someone casting out devils in the name of Christ and had forbidden him “because he followed not” with them. In response, they heard, “Forbid him not: for he that is not against us is for us” (Luke 9:50). Those words have naturally been the watchword for those who rejoice whenever Christ is preached, in every way and by whatever organization.

In reality, however, the two formulas simply present the opposite poles of the same truth. In the great struggle between light and darkness, good and evil, God and the enemy of God, there is no neutrality. The man of whom the two disciples complained was fighting against the devil in the name of Christ and was therefore with Him. The Pharisees, on the other hand, were hindering and slandering that work and were therefore on the side of Satan. They were not gathering in God’s harvest of souls; therefore, they were scattering and wasting.