ב"ה, ט' תמוז, תשי"ב
אצטער על שאינו מזכיר במכתבו דבר ע"ד שידוכים, וידוע לו דעתי בזה מכבר שאמרו רז"ל שדרכו של איש לחזור, והמשל הוא ממי שאבדה לו אבדה, ורואים במוחש אשר בעל האבדה אינו מחכה במקומו ובביתו עד שיבוא פב"פ ויאמר לו, מצאתי חפץ, ואולי שלך הוא, אלא הוא יוצא ממקומו, וגם אפי' כמרז"ל חתן חות דרגא ומחפש אבדתו. והשי"ת יצליחו.
B"H, 9th of Tammuz, 5712.
I am saddened that you did not mention anything about shidduchim in your letter. You already know my opinion on this matter from before, as our Sages say that it is the way of a man to seek out [a match].
The analogy is to someone who has lost an object. We see clearly that the owner of the lost item does not wait in his place or at home until someone comes face-to-face and says to him, 'I found an object, and perhaps it is yours.' Rather, he goes out from his place—even as our Sages say: 'the groom ascends a step and searches for his lost item.'
May Hashem grant you success.
Summary
The Rebbe teaches that one must actively pursue finding a marriage match, just as someone who has lost something does not wait passively but searches for it with effort and initiative.