This instance of Christ conferring the priesthood is interesting because it is so similar to the current pattern: he gave them the Melchizedek Priesthood through the laying on of hands and commissioned them to give the gift of the Holy Ghost to the multitude. But what may be more interesting is how this ordinance differs from the current practice. The Savior instructed the twelve to pray to the Father before they would receive this power. What is the significance of this instruction?
The message seems to be that while the priesthood can be conferred by an ordinance, the power of the priesthood cannot be obtained without the exercise of faith. This is according to the ancient pattern, for the patriarchs received the priesthood through faith, Behold it was by faith that they of old were called after the holy order of God (Ether 12:10). Furthermore, we are reminded of the other Twelve, who had failed to cast out a certain devil because their faith was lacking. They were told, this kind goeth not out but by prayer and fasting (Matt 17:21). Apparently, the fact that they had the priesthood was not enough. They needed to exercise more faith in order to use God's power. While we know that, The powers of heaven cannot be controlled nor handled only upon the principles of righteousness (DC 121:36), we need to remember that faith is one of the most important of these principles.