The mother and brother gather around Rivekah on the morning she is to leave, and they speak a blessing that the Jewish people have been whispering over their daughters ever since. Targum Pseudo-Jonathan on Genesis 24:60 preserves it with a few careful additions.
"Hitherto thou wast our sister; and now thou art going and art wedded to the righteous." The Targum adds a word the plain Torah leaves implicit: to the righteous. She is not marrying into a wealthy family. She is marrying into a righteous one. That is the benediction's first claim.
Then: "so prosper thou, that from thee may come thousands of myriads; and may thy sons inherit the cities of those who hate them." Thousands of myriads. A phrase large enough to cover every Jewish generation still waiting in the shadow of her womb.
Tradition recites a version of this blessing over brides at weddings to this day. The line about inheriting the gates of enemies is quoted nearly verbatim at the bedeken, the veiling ceremony before a Jewish wedding. Rivekah's family — idol-cluttered, complicated, just one death into new grief — nevertheless produces a blessing so clean the tradition has never been able to improve on it.
The Maggid's observation is this. Sometimes the most mixed households generate the purest prayers. Laban will fleece Jacob later. The brother is not the hero of this book. But the sentence he speaks here, with his mother at his side, is a sentence the covenant people are still repeating thousands of years later. God can use any mouth to send a daughter out loved.