A story taken from the recently published book: "The Mazkir", by Uri Kaploun:
Only on extremely rare occasions did the Rebbe reveal to those who consulted him the heavenly dynamics that underlay his movements, such as the decisions that he had been called upon to make. R. Leibel once related the following stunning instance of this. It involved the son of a Hungarian family from Williamsburg who had moved him from the Yeshiva in which he had been studying, after which he had begun to study in a Chabad Yeshiva.
"When this young man was of marriageable age, he asked the Rebbe whether he should follow up a certain Shidduch that had been proposed to him and received a positive answer. He told his parents of this, and after a few days of inquiries about the young lady in question, his mother informed him that she and her husband held that the proposal was not appropriate for him.
"Since he received the Rebbe's approval to proceed, the couple proceeded to meet. Eventually, when they were ready to clinch the Shidduch, the Bochur wrote again to the Rebbe requesting his blessing for that major step. Even though he told the Rebbe that his parents disapproved of this Shidduch, the Rebbe gave it his consent, together with his blessing that it should be sealed at a good and auspicious time.
"When he reported this to his parents, they assured him that they would not participate in the wedding nor in the expenses involved."
When R. Leibel related this episode, he cited the teachings of the Rama that on two decisions a person is not obligated to ask anyone but himself - whom he should marry and where he should study. However when the parents of the Bochur were told this, they remained unimpressed.
"About a week later, the mother arrived at 770, and before the astonished eyes of all those who were present, she slapped her son's face, and ordered him not to marry that young lady.
"Some of the Bochurim who witnessed that scene suggested to the mother that if she had complaints she should direct them not to her son but to the Rebbe, whose counsel and blessing her son had followed. And Indeed, she went straight to the Mazkirus, where I duly arranged a Thursday night appointment for herself and her husband. When that time came, I observed a group of Bochurim waiting anxiously outside, eager to hear how things would work out."
"A quarter of an hour later, when the parents came out of the Rebbe's room, the mother said: "We agree to the Shidduch with all our heart."
"What happened?" they all chorused.
"The mother explained excitedly: 'As soon as we went in, my husband listed the reasons for our objection. The Rebbe then listened to what I had to say and then said: 'Before I give an answer about a Shidduch, I check through all the Shidduch-books Up Above, to see whether or not the proposed Shidduch is appropriate. Only then do I given an answer. The Bochur wrote and asked whether he should inquire about a certain proposal and then to meet. After checking all those Shidduch-books, I answered in the affirmative. When I received his second letter, which said that he and the young lady were prepared to clinch the Shidduch but that you objected, I checked once again through all of those Shidduch-books Up There and found no problem.
"The mother deeply moved, concluded aloud: "Here sits a Tzaddik who goes Up There to check through all the books before he gives an answer. After that, I haven't got a word to say!"