In a tweet by Matthew Schmitz on Twitter I came across a striking quotation, attributed to Basil of Ancyra / Basil the Great. Enquiry quickly showed that in fact it came from a work by medieval writer Peter Damian, complete with attribution to Basil.
The publication I found was Peter Damian, Book of Gomorrah: An eleventh-century treatise against clerical homosexual practices, tr. Peter J. Payer, Wilfred Laurier University Press, 1982, p.60-61. This reads:
However, since we have taken care to use two testimonies from one sacred council, let us also insert what Basil the Great thinks of the vice under discussion so that “on the testimony of two or three witnesses every word shall be established.” He says:
“A cleric or monk who seduces youths or young boys or is found kissing or in any other impure situations is to be publicly flogged and lose his tonsure. When his hair has been shorn, his face is to be foully besmeared with spit and he is to be bound in iron chains. For six months he will languish in prison-like confinement and on three days of each week shall fast on barley bread in the evening. After this he will spend another six months under the custodial care of a spiritual elder, remaining in a segregated cell, giving himself to manual work and prayer, subject to vigils and prayers. He may go for walks but always under the custodial care of two spiritual brethren, and he shall never again associate with youths in private conversation nor in counselling them.” 
67. The text is from Regula Fructuosi, ch. 16 (PL 87, 1107A). English translation, C. W. Barlow, “Rule for the Monastery of Compludo”, in The Fathers of the Church, 63 (Washington, DC, 1969), 169.
The Fathers of the Church volume is in fact entitled Iberian fathers: volume 2 : Braulio of Saragossa, Fructuosus of Braga / translated by Claude W. Barlow, 1969. From this I learn that Fructuosus produced two monastic rules, a Regula monachorum Complutensis, the Rule of the monks of Compludo, and another more general rule. The former appears in the PL 87, 1099-1132, and Dr Barlow comments ruefully (p.148), “This edition is far from satisfactory, often corrupt, but no more recent study of the text has been made from the manuscripts known to exist in Spain and Portugal.” Chapter 16 is translated on p.168-9 and reads in full:
16. Monks who lie, steal, strike, or swear falsely in a manner not fitting a servant of Christ must first be verbally chided by their elders to withdraw from their vice. Then, if one has not yet reformed, he shall be brought three times before the brothers and warned to desist completely. If he still does not change, he shall be severely flogged and shall be secluded in a cell under the rigors of penance, having been sentenced to excommunication for three months; he is to be fed six ounces of barley bread each evening and allowed a small measure of water. Anyone found drunk in the monastery shall also be subject to the aforementioned sentence; likewise, any who write letters or receive them from others without the permission of the abbot or prior. A monk who is too attentive to boys or young men or has been caught kissing or indulging in other indiscreet acts, after the case has been openly proved by truthful accusers and witnesses, shall be publicly thrashed; he shall lose the crown which he wears and with head shaven shall be exposed to shame and disgrace; all shall spit in his face and heap their accusations upon him; he shall be bound in iron chains and held in narrow confinement for six months; and shall be given a small amount of barley bread in the evening on three days of each week. After this time is past, for the next six months he shall live in a separate cell under the watchfulness of a spiritual elder and shall be content with manual labor and continual prayer; he shall seek pardon by vigils and tears and abject humility and penitential laments. He shall walk in the monastery under the constant care and watch of two spiritual brothers, and shall never thereafter join the young in private conversation or companionship.
That’s pretty conclusive.
So the passage attributed to St Basil in fact comes from chapter 16 of a monastic rule attributed to Fructuosus of Braga (d.665 AD). It has nothing to do with Basil; not even the monastic rule attributed to him.
The twitter post itself attracted some erudite comment. This from “Matthew Cullinan Hoffman’s note on this quotation, from his translation of St. Peter Damian’s Liber Gomorrhianus”
This quotation, which Damian’s source (probably Burchard’s Libri Decretorum, lib. 17, cap. 35; PL 140, 925D) attributes to St. Basil, is in reality a slightly truncated form of a penalty prescribed for monks by St. Fructuosus of Braga (d. 665) (Regula Monachorum, cap. 16; PL 87, 1107A-B . A section of it also appears in the decrees of Ecgbert, bishop of York (d. 766) (PL 89, 387D), who correctly attributes it to Fructuosus, but in the later Collectio Canonum Quadripartia, (a manual used and referenced widely during the latter part of the early middle ages in France, England, and Italy), it contains no attribution. By the tenth century, collections of canon law such as Burchard’s were incorrectly attributing it to Basil.
Of course as a non-medievalist, I wouldn’t attempt to comment on this background; but it is very useful to tie this down.
Update: My thanks to two correspondents who supplied me with the FOC 63 volume!