St Isaiah the Solitary lived in asceticism at Scetis in Egypt and then in Palestine, dying in Gaza in about 491. He is mentioned in Sts Barsanuphius and John's book as a man of outstanding holiness (Answers: 240, 252, 311 etc.). He wrote much on the rebuttal of demonic provocations and on the need to be attentive to the conscience but few of his writings still exist, the majority having been destroyed. The Church commemorates the feast of St Isaiah the Solitary on July 3.  

Prayer and asceticism are useless to a man who conceals within himself malice towards his neighbour and the desire for revenge.

'Watch with all your strength that your mouth does not speak one thing and your heart contain something quite different.' 'The crown of good works is love; the crown of the passions is the justifying of one's sins.'

St Isaac of Syria (7th century)