John Gill Commentary Mark 3:15

"and to have authority to cast out demons:" — Mark 3:15 (ASV)

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.