John Cassian, Conferences XI–XVII XV.9: How uprightness of life is of more importance than the working of miracles

And of those cures it was said to the blessed Apostles: “Rejoice not that the devils are subject to you.” For this was wrought not by their own power, but by the might of the name invoked. And therefore they are warned not to presume to claim for themselves any blessedness or glory on this account as it was done simply by the power and might of God, but only on account of the inward purity of their life and heart, for which it was vouchsafed to them to have their names written in heaven.