Blasphemy

Those unclean and unspeakable thoughts (of blasphemy) come at us when we are praying, but, if we continue to pray to the end, they will retreat, for they do not struggle against those who resist them.

Anyone disturbed by the spirit of blasphemy and wishing to be rid of it should bear in mind that thoughts of this type do not originate in his own soul but are caused by that unclean devil who once said to the Lord: "I will give you all this if only you fall down and adore me" (Matthew 4:9). So let us make light of him and pay no regard whatever to his promptings. Let us say: "Get behind me, Satan! I will worship the Lord my God and I will serve only him" (Matthew 4:10).

~ Saint John Climacus in Ladder of Divine Ascent

John Climacus (525 – 30 March 606), also known as John of the Ladder, John Scholasticus and John Sinaites, was a 7th century Christian monk at the monastery on Mount Sinai. He was born in Syria, and came to the monastery when he was about 16 years old. After the death of his mentor, Martyrius, John, withdrew to a hermitage at the foot of the mountain. In 600, when he was about seventy-five years of age, the monks of Sinai persuaded him to put himself at their head. He acquitted himself of his functions as abbot with the greatest wisdom, and his reputation spread so far that pope Gregory the Great wrote to recommend himself to his prayers, and sent him a sum of money for the hospital of Sinai, in which the pilgrims were wont to lodge. Four years later he resigned his charge and returned to his hermitage to prepare for death. He wrote a number of instructive books, including the Scala (Climax) or Ladder of Divine Ascent, composed at the request of John, Abbot of Raithu, a monastery situated on the shores of the Red Sea.