The Council in Trullo (Quinisext Council, 692 AD)

Those who in town or in villages wish to go away into cloisters, and take heed for themselves apart, before they enter a monastery and practise the anchorite’s life, should for the space of three years in the fear of God submit to the Superior of the house, and fulfil obedience in all things, as is right, thus shewing forth their choice of this life and that they embrace it willingly and with their whole hearts; they are then to be examined by the superior (προέδρος) of the place; and then to bear bravely outside the cloister one year more, so that their purpose may be fully manifested. For by this they will shew fully and perfectly that they are not catching at vain glory, but that they are pursuing the life of solitude because of its inherent beauty and honour. After the completion of such a period, if they remain in the same intention in their choice of the life, they are to be enclosed, and no longer is it lawful for them to go out of such a house when they so desire, unless they be induced to do so for the common advantage, or other pressing necessity urging on to death; and then only with the blessing of the bishop of that place.

And those who, without the above-mentioned causes, venture forth of their convents, are first of all to be shut up in the said convent even against their wills, and then are to cure themselves with fasting and other afflictions, knowing how it is written that “no one who has put his hand to the plough and has looked back, is fit for the kingdom of heaven.”

Ancient Epitome of Canon XLI.

Whoever is about to enter a cloister, let him live for three years in a monastery, and before he is shut up let him spend one year more, and so let him be shut up. And he shall not then go forth unless death or the common good demands.

This canon, so far as it sets forth the necessity of probation before admission to the Anchorite life, synods in after-years frequently approved, taught as they were by experience how perilous a matter it is to admit without sufficient probation to this solitary life and state of separation from the common intercourse with his fellow men. Vide the Synod of Vannes (about a.d. 465) canon vij., of Agde chap. lxxviij., of Orleans the First can. xxij., of Frankfort can. xij., of Toledo the Seventh can. v., and the Capitular of Charlemagne To monks, Chap. ij.