The problem, of course, is that the reason that Leah publicly says at the bris is wrong; what happened to שכר שכרתיך? Why is the שכר for נתתי שפחתי לאישי? Many commentators note that the name implies two reasons:
The whole אלי תבוא כי שכר שכרתיך is not the sort of thing one announces in public. The giving of the maidservant, however, was known.
The question, then, is why Leah felt she deserved a reward for allowing Zilpah to marry Yaakov. The answer is that is “giving of the maidservant” was different from Rachel’s.
I would understand this “יודעות שעתיד יעקב להעמיד י״ב שבטים” not as a literal prophecy, but as the hope that this generation would be the one that would be the beginning of the nation.
Twelve tribes in תנ״ך is symbolic of the start of a new nation; the transition from individuals to a community. יעקב wanted to end the בחירה process that had limited all of humanity to just אברהם then limited his children to just יצחק then limited his children to just יעקב.
We’ve talked before about how the text emphasizes the parallel יציאת לבן and Yaakov’s return to ארץ כנען, and the “real” יציאת מצרים.
Yaakov hoped that his return to the land would be the fulfillment of the ברית בין הבתרים.
So Leah’s חסד was in saying that she was not having more children; Rachel is not having children and Yaakov needs more children. She allows Yaakov to take another wife, so that there would be another child in the family, even if that child would not be hers. It was the same חסד as Sarah’s.
Note that this is not The Handmaid’s Tale—the שפחה is not a surrogate but another wife; the child would not be Sarah’s or Leah’s. That is why it is a חסד. This was Rachel’s mistake.
In the context of the Torah, this חסד is the woman’s equivalent of יבום.
While I noted that Rachel got this wrong initially, we see that she also eventually acts with חסד. (This is based on an insight from Rabbi David Fohrman.)
We all know the haftorah for Rosh Hashana (second day):
יש שכר לפעלתך. What is the פעולה that ה׳ is rewarding? The פשט, reading the text very locally, would be Rachel’s מבכה על בניה:
And we all know the aggadah:
But that’s not in the text. What פעולה do we see for Rachel that ה׳ should have pity on Israel? What is unique about Rachel? There’s a hint in the midrash:
Note the pun: כי יששכר לפעלתך→כי יש שכר לפעלתך. there is a יששכר because of your actions.
Rachel allows Leah to have another child with Yaakov and gives up her claim to יששכר. That חסד will lead to שבו בנים לגבולם, במהרה בימינו.