To have power to heal - and to cast out devils - The business of a minister of Christ is,

1st. To preach the Gospel.

2dly. To be the physician of souls. And,

3dly. To wage war with the devil, and destroy his kingdom.

And to have power to heal sicknesses,.... All manner of corporeal diseases that attend men and women:

and to cast out devils; from such who were possessed with them: that is, he chose and appointed them to be his apostles, with a view of conferring such powers upon them hereafter; for as yet, they were not vested with them, nor sent out to exercise them; no, not till near twelve months after.

To have power (ἔχειν ἐξουσίαν)

Note that he does not say to preach and to cast out, but to preach and to have authority to cast out. The power of preaching and the power of exorcising were so different that special mention is made of the divine authority with which they would need to be clothed. The power of driving out demons was given that-they might apply it in confirmation of their teaching. Compare Mark 16:20.

And to have power to heal sicknesses, and to cast out devils:

3:13-21 Christ calls whom he will; for his grace is his own. He had called the apostles to separate themselves from the crowd, and they came unto him. He now gave them power to heal sicknesses, and to cast out devils. May the Lord send forth more and more of those who have been with him, and have learned of him to preach his gospel, to be instruments in his blessed work. Those whose hearts are enlarged in the work of God, can easily bear with what is inconvenient to themselves, and will rather lose a meal than an opportunity of doing good. Those who go on with zeal in the work of God, must expect hinderances, both from the hatred of enemies, and mistaken affections of friends, and need to guard against both.