Some early Christians went to church and listened for the words of scripture that were being sung when they entered the church as a random means of predicting the future and God's will (along the lines of the Jewish Bath Kol form of divination), but the Sortes was done more formally, by casually opening the Holy Scripture and reading the first words to come to hand, with these words being taken to foretell the inquirer's fate. Doing so was often a public event, and sometimes accompanied by ceremonies (such as the 7th century emperor Heraclius ordering 3 days' public fast before a consultation as to whether or not he should advance or retreat against the Persians - he took the text that arose as divine instruction to winter in Albania). Since full copies of the Christian Bible were rare before printing was invented, the lots usually used the Psalms, the Prophets, or the four Gospels.
A French writer, in 506, says, "this abuse was introduced by the superstition of the people, and afterwards gained ground by the ignorance of the bishops.", as is shown by Pithon's Collection of Canons, which contains some forms under the title of The Lot of the Apostles. These were found at the end of the Canons of the Apostles in the Abbey of Marmousier, and various canons were made at later councils and synods (such as the councils of London under Archbishop Lanfranc in 1075, and Corboyl in 1126) against the Sortes as superstition. However, they were still occurring in the time of St Francis who, in denying himself any possessions except coats and a cord, wanted to check if he was still allowed to own books. He prayed and then drew Mark, chapter IV, "Unto you it is given to know the mystery of the kingdom of God; but unto them that are without, all these things are done in parables", which he took to mean that he was neither allowed books nor needed them.
A Peter of Toulouse, who had sworn on the Bible that accusations of heresy against him were false, was immediately afterwards convicted by the Sortes when a bystander grabbed the Bible and opened it randomly at the words of the Devil Legion to Jesus, "What have we to do with thee, thou Jesus of Nazareth?", which he adjudged to mean that Peter had nothing to do with Jesus.
St. Francis of Assisi, to seek divine guidance, is said to have thrice opened to a random page of the book of Gospels in the church of St. Nicholas. Each time he opened to a passage in which Christ told His disciples to leave their earthly belongings and follow Him.
So was I speaking and weeping in the most bitter contrition of my heart, when, lo! I heard from a neighbouring house a voice, as of boy or girl, I know not, chanting, and oft repeating, "Take up and read; Take up and read." Instantly, my countenance altered, I began to think most intently whether children were wont in any kind of play to sing such words: nor could I remember ever to have heard the like. So checking the torrent of my tears, I arose; interpreting it to be no other than a command from God to open the book, and read the first chapter I should find. For I had heard of Antony, that coming in during the reading of the Gospel, he received the admonition, as if what was being read was spoken to him: Go, sell all that thou hast, and give to the poor, and thou shalt have treasure in heaven, and come and follow me: and by such oracle he was forthwith converted unto Thee. Eagerly then I returned to the place where Alypius was sitting; for there had I laid the volume of the Apostle when I arose thence. I seized, opened, and in silence read that section on which my eyes first fell: Not in rioting and drunkenness, not in chambering and wantonness, not in strife and envying; but put ye on the Lord Jesus Christ, and make not provision for the flesh, in concupiscence. No further would I read; nor needed I: for instantly at the end of this sentence, by a light as it were of serenity infused into my heart, all the darkness of doubt vanished away.