Numbers 11:28 - Ellicott's Commentary On The Whole Bible

My lord Moses, forbid them. — The motive which prompted Joshua in making this request appears to have been similar to that which led St. John to forbid the man to cast out devils who did not follow with the Apostles (Mark 9:38-39; Luke 9:49-50). But as the man did not cast out devils in his own name, but in that of Christ, so in this case Eldad and Medad prophesied in virtue of the spirit which rested upon them from above, of which the Holy Ghost, not Moses, was the giver. The motives which deterred Eldad and Medad from going to the tent of meeting are unknown. The history teaches the freeness and the sovereignty of the Holy Spirit’s influences, as afterwards did that of Cornelius, when the Holy Ghost fell upon him and upon those who were with him, previously to the reception of baptism, and they spoke with tongues and magnified God (Acts 10:44-48).