I'm interested in knowing whether martyrs are promised 72 virgins in heaven. I've already searched this site, and the question has not come up before.
According to this hadith, a myrtyr is given 72 wives (not virgins) among 5 other othings
That the Messenger of Allah () said: "There are six things with Allah for the martyr. He is forgiven with the first flow of blood (he suffers), he is shown his place in Paradise, he is protected from punishment in the grave, secured from the greatest terror, the crown of dignity is placed upon his head - and its gems are better than the world and what is in it - he is married to seventy two wives along Al-Huril-'Ayn of Paradise, and he may intercede for seventy of his close relatives.
Could virgin come from a non authentic source? It is possible. Will update the answer if I find something relevant.