What is the meaning of the opening phrase of the Pasuk? Why does it say "Milel," and not the more common 'Diber'?
Rashi, Rashbam, Da'as Zekenim #1, Targum Onkelus and Targum Yonasan: It is an expression of praise 1 and it means, 'How praiseworthy is the One who told Avraham that they would have a child, and Who kept His promise. It uses the word "Milel," because the Gematriya of 'Milel' is 100 (Avraham's age when Yitzchak was born). 2
Rashbam: They will realize the greatness of the G-d, Who promised Avraham that he would bear a son to Sarah in their old age, and they will know that there is none who can compare to Him.
Ramban: Who would have dreamt to tell Avraham that Sarah would suckle children (even to console him), since it was so far removed from the realm of possibility. 3
Da'as Zekenim #2: It is an expression of Melilos (moist grain) - who would have said that Avraham will have moisture, i.e. seed?!
The Ramban maintains that "Mi" in this sense is only used derogatively (See for example Shoftim 9:28). Refer to 21:7:1.1:1.
Riva understands that "Milel" teaches that he was 100. A verse explicitly says so! Rather, it teaches that it was after 100 years were complete.
According to the Ramban, this is also the opinion of Targum Onkelus.
Why does the Torah write "Banim" (in the plural)?
Rashi: Because at the Se'udas Bris, the princesses all brought their babies, and Sarah suckled them all.
What was the purpose of that miracle?
Rashi: It was in answer to those who claimed that Sarah did not bear a son, but that she brought home a waif that she found in the street. 1
QUESTIONS ON RASHI
Rashi writes: "'Who had uttered' (Mi Milel) - An expression of praise and distinction" [to HaSh-m, Who had fulfilled His promise]. Ramban asks - "Who is..." is often used rhetorically, as an expression of derision (see Shoftim 9:28)?
Gur Aryeh: We could explain the verse rhetorically, 'Who ever thought of telling Avraham, that Sarah would one day nurse children? It was inconceivable!' But then why mention Avraham? 1 Also, the verse should then use the word, 'Amar,' which can include thought, rather than 'Milel.' Rashi therefore explains it as praise to HaSh-m.
Gur Aryeh: To answer for Ramban, perhaps the verse mentions Avraham because he was more pained by the lack of children, for Peru u'Revu is incumbent upon men.
