Mark 6:13

‘And they cast out many devils, and anointed with oil many that were sick and healed them.'

Their ministry was accompanied by successful acts of power. Evil spirits were cast out, and as well as that they healed the sick by the anointing with oil (compare James 5:14 where it is ‘in the Name of the Lord'). This anointing with oil demonstrated the separation of the person in question to God as in the Old Testament. They were healed because they responded to Him in faith and became His. Healing in God's name put them in further debt to God, signifying that they were henceforth to live for Him and obey Him. They became His property. It also distinguished the ministry of the Apostles from that of Jesus, He healed through His own power and authority, whilst they healed through His power and authority. Thus the oil was also symbolic of the Anointed One in Whose Name they healed.

It is true that oil was also at this time seen as a healing medicament (compare Luke 10:34). But elsewhere when it was used it was seen as working gradually. There was nothing of that idea here. Here the thought was rather that these people were being set apart to God, and committed to the Name of the Anointed One. Healing could only be expected where there was a submissive heart (compare Mark 2:1).

This ministry of the Apostles was vital preparation for their future. They preached, and they preached effectively, what they had heard from Jesus, thus sealing it in their own minds; they would then begin to appreciate how little they knew of what they should know and would thus in future pay even more attention to Jesus' ministry (no one learns more, or is more aware of his own need to be taught, than he who genuinely seeks to teach others); and their words prepared men for the time when Jesus Himself would arrive to preach among them, and laid the foundation for the future message. Jesus clearly saw the mission as a success. Had He not done so He would not have later sent out the seventy (Luke 10:1). There would, of course, be a limit to what the disciples taught. They still had very mistaken ideas about the Kingly Rule of God, as John had had before them. But they could not go wrong on the central message, that the Kingly Rule of God was about to break in on men. Perhaps it was their over-enthusiasm that resulted in five thousand men seeking them out along with Jesus in the desert place.