Mark 9:40

For he that is not against us is on our part.

Jesus spoke these words when John reported that he and James had forbidden a man who was casting out devils in His name because the man did not join their company, and they thought they were right to forbid him. John sincerely told Jesus what they had done, having decided the man had no right to do that work because he did not immediately join them and was not an acknowledged follower. Christ reproved them for forbidding him.

Such a worker must not be forbidden, because no one who does a miracle in Jesus' name can lightly speak evil of Him. One who is not against Christ and His followers is for them and on their side, even if only in a small way friendly to Christ. Those who are not opposing Christ are on His side.

Therefore service done in Christ's name must not be rejected, despised, discouraged, hindered, obstructed, or treated as hostile or as an enemy merely because the worker does not belong to the disciples' company, does not follow them, does not follow their plans, works differently, or does not share all their opinions, and not even a humble servant of Christ is to be obstructed. A willing worker must not be repulsed, and those who cannot read another's motives must not shut off the light God would send through that person. Disciples must welcome service done in His name rather than guard their own standing.

The attempt to forbid arose from jealousy and a desire for preeminence, self-preference, and guarding their own standing, showing a narrow, exclusive, sectarian, and restrictive spirit. Though the disciples thought they were acting for the Lord's honor, they were jealous for themselves. When reproved, they acknowledged their error and accepted the reproof.

The verse requires humility, tenderness, forbearance, and broad and far-reaching sympathy like Christ's toward sincere Christians outside one's own faith, welcoming willing service, treating others fairly rather than excluding them without cause, not repulsing willing workers, not shutting off light God would send through them, and ruling out bigotry, self-righteousness, and letting jealousy hinder Christ's work. Disciples must not reject others or claim authority over those outside their company by deciding who may join their number, which shows the danger of self-sufficiency and of leaders seeking too much authority. Workers whom God has appointed should not be hindered or forbidden, for even people who were once enemies can become valuable helpers who advance the work through their means and influence.

A work is not on Christ's side merely because it aims to help people. The slum work in view was not gathering with Christ because it drew the person away from the specific duty God had assigned at the Sanitarium and led him to take on too many responsibilities.