"Nor May They Marry..." ( v. 7)
"In all matters of matrimony, the happiness of tow partners is involved, and if there is any issue, the happiness of children and future generations is at stake. Obviously, a marriage which has been prohibited by the Creator and Master of the Universe is one that cannot possibly be a happy one, and is certain to be harmful to both parties concerned. In other words, if the said Kohen [priest] has any feelings for the divorce in question, he should realize that his marrying her would expose her to untold harm, not only in the after-life and in spiritual sense, but also in this life, and even in a physical and material sense. The fact that this may be beyond one's comprehension is immaterial, for it is certain that the Creator of the world knows best what is good for His creatures, and since He has so strictly prohibited such a marriage, there can be no doubt that it is harmful. Therefor, even on humanitarian grounds, the said Kohen, if he has any feeling for the said divorce, should give up the idea and avoid causing himself and her irreparable damage, physically and spirituality."
(Excerpt from a letter written by the Rebbe on 19th Sivan 5717)