The holy father Dominic also had another beautiful way of praying, full of devotion and grace. After the canonical hours and the grace which is said in common after meals the father would go off quickly to some place where he could be alone, in a cell or somewhere. Sober and alert and anointed with a spirit of devotion which he had drawn from the words of God which had been sung in choir or during the meal, he would settle himself down to read or pray, recollecting himself in himself and fixing himself in the presence of God. Sitting there quietly, he would open some book before him, arming himself first with the sign of the cross, and then he would read. And he would be moved in his mind as delightfully as if he heard the Lord speaking to him. As the Psalm says, ‘I will hear what the Lord God is saying in me, because he will speak peace to his people and upon his saints, and to those who turn to him with all their heart’ (Psalm 84:9). It was as if he were arguing with a friend; at one moment he would appear to be feeling impatient, nodding his head energetically, then he would seem to be listening quietly, then you would see him disputing and struggling, and laughing and weeping all at once, fixing then lowering his gaze, then again speaking quietly and beating his breast. If anyone was inquisitive enough to want to spy on him secretly, he would find that the holy father Dominic was like Moses, who went into the innermost desert and saw the burning bush and the Lord speaking and calling to him to humble himself (Exodus 3:1ff). The man of God had a prophetic way of passing over quickly from reading to prayer and from meditation to contemplation.
When he was reading like this on his own, he used to venerate the book and bow to it and sometimes kiss it, particularly if it was a book of the gospels or if he was reading the words which Christ had spoken with his own lips. And sometimes he used to hide his face and turn it aside, or he would bury his face in his hands or hide it a little in his scapular. And then he would also become anxious and full of yearning, and he would also rise a little, respectfully, and bow as if he were thanking some very special person for favors received. Then, quite refreshed and at peace in himself, he would continue reading his book.
From a 13th century text, The Nine Ways of Prayer of St. Dominic – link.