(48:15) “And they (the angels) said to him: Where is Sarah,
your wife?” (Bereishis
18:9) - the letters איו
have a dot over them, the letter ל
does not have a dot place over it. Said R. Shimon ben Elazar: Wherever
you find that the written (undotted) letters outnumber the dotted
letters, you expound the written letters. And if the dotted letters
outnumber the written letters, you expound the dotted letters. Here,
where the dotted letters outnumber the dotted letters, you expound the
dotted letters איו - “Where is Avrohom”.
Said R. Azariah: Just like they said “Where is Sarah”, so too they said to Sarah “Where is Avrohom”.
“And he (Avrohom) said: Behold, in the tent” (Bereishis 18:9). This is what is written “Blessed more than the women shall be Yael, the wife of Chever the Kenite, more than the women in the tent shall she be blessed” (Shoftim 5:24). R. Elazar and R. Shmuel bar Nachman - R. Elazar said: More than the generation of the women of the wilderness who dwelt in tents, as it says “each man at the entrance to his tent” (Bamidbar 11:10). And why should she be more blessed than them? Because they bore children and caused the continued existence of the world, but how would this have helped them - if not for her (Yael) they would have already perished (because of Sisera)! R. Shmuel bar Nachman said: More than the Matriarchs (who all dwelled in tents), because they bore children…but if not for her they would have already perished!
An explanation of the first part of this Midrash can be found in the sefer Binyan Ariel.