13 “And the lust of the eyes:” by “the lust of the eyes,” he means all curiosity. Now how wide is the scope of curiosity! This it is that works in spectacles, in theatres, in sacraments of the devil, in magical arts, in dealings with darkness: none other than curiosity. Sometimes it tempts even the servants of God, so that they wish as it were to work a miracle, to tempt God whether He will hear their prayers in working of miracles; it is curiosity: this is “lust of the eyes;” it “is not of the Father.”
If God has given the power, do the miracle, for He has put it in your way to do it: for think not that those who have not done miracles shall not pertain to the kingdom of God. When the apostles were rejoicing that the demons were subject to them, what said the Lord to them? “Rejoice not in this, but rejoice because your names are written in heaven.” In that would He have the apostles to rejoice, wherein you also rejoice. Woe to you truly if your name be not written in heaven!
Is it woe to you if you raise not the dead? Is it woe to you if you walk not on the sea? Is it woe to you if you cast not out demons? If you have received power to do them, use it humbly, not proudly. For even of certain false prophets the Lord has said that “they shall do signs and prodigies.” Therefore let there be no “ambition of the world:” Ambitio sæculi, is Pride. The man wishes to make much of himself in his honors: he thinks himself great, whether because of riches, or because of some power.
Source: Homilies on the First Epistle of John (New Advent)