Menachem Begin, of blessed memory, met several times with the Rebbe in his private study (both prior to and after becoming the Israeli Prime Minister).
At the end of one of these audiences, the Rebbe turned to Begin and asked him if he would do him a personal favor. Begin replied affirmatively.
The Rebbe told him that he had received a letter from a French girl's parents who wrote in great pain about their daughter who was dating a non-Jew and was planning to marry him. The parents had tried every thinkable way to separate the two, but with no success. Feeling hopeless, they turned to the Rebbe for help and advice.
"I am sure," the Rebbe told Begin, "that if a well-known individual as yourself, especially as you speak French, will speak to her about her choice in marriage, she will respect your words, and it will influence her in the correct direction."
Begin agreed to fulfill this mission. The Rebbe gave him the name, address, and phone number of the girl, and told him that he should send him the bill for the stopover in France.
Begin traveled to France and spoke, with words straight from his heart, to the young girl who was making the decision of her life. His words entered her heart, and she decided to move to Israel, thus automatically ending her relationship with the non-Jew.
The Rebbe covered the expenses for the stopover in France, and the girl married a Jew and today lives in Jerusalem.