פרשת לך לך תש"ל - הבשורה על הולדת יצחק

Cassuto, The Documentary Hypothesis, Chapter 3, "On the Names of God":

The name of the Lord (the Tetragrammaton) [is selected] by the Torah when speaking about the God of Israel with reference to His people, or to the forefathers of His people; and the name, Elokim, when it is speaking about his Godliness with reference to someone who is not connected to the chosen people. (And see his words at length in the guidance sheet.)

R. David Pardo, Maskil LeDavid (commentary on Rashi):

One should not ask, "[Since] the verse wrote, 'My covenant,' in the singular, how could Rashi say two [things]?" For both of them are one [item], as Rashi himself says later on...

R. Yosef Ibn Kaspi, Tirat HaKessef II:3 (p. 88):

And the fourth benefit that we learned from this (Chapter 17 of Genesis) is that which the earlier Sages, may their memory be blessed, commanded us. And that is that we should not have faith in anything unless we have a sign about it. And behold this matter is very subtle, as we might hold in our minds to think a sign to be conclusive when it is not... And behold this question that we mentioned is fitting to be dependent towards 'more or less,' based on the preciousness of the concept [to be determined]. Hence when Abraham arrived at the fourth level of his comprehension with this vision – and this is in what is written (Genesis 9:15), "And God said to Abraham, 'Your wife, Sarai, etc.'" – God then revealed secrets of existence to him, which He had not revealed to him up until now. And this is what He informed him now: That in spite of his being a hundred years old and Sarai being ninety years old, the two of them would bear a son. For it [would have been] likely that that which preceded this (9:6), "And I will make you fruitful," was about Yishmael; especially in that it was a greater wonder with Sarah – as Abraham had more children with Keturah much later. Hence because this matter was such a wonder, a little doubt entered his heart, and he said, "Can a man of a hundred years..." And God forbid that he rejected this, as it is part of perfection not to begin to reject something unless there is a sign for its opposite. Rather he was contemplating in his heart and going back and forth whether this is possible with God who is the Master of wisdom and intellect. As his laughter was not like Sarah's laughter; but rather the laughter was mixed with awe – and 'in the place of joy there was trepidation.' And even though this is not mentioned, the proof about [the nature of his laughter] is that he was not apprehended about it, as happened to Sarah. And we have already established that one matter itself can go out to two contradictory actions or goals. And his saying, "Can a man (Haleven)" with a [letter] hay [indicating a] question does not necessitate negation [of the proposition], as mentioned by Rashi.¹ Rather it like the hay that sometimes comes as a question and sometimes comes as a wonder about something slightly possible. For that which is [almost not] possible is treated as impossible in many places, by way of generalization... And I return to our intention and say that since this secret matter was very deep and very precious, Abraham was concerned about [whether he could rely upon] his ideas and his intellect. So he did not fully believe it, but he also did not reject it. Rather he said what he said, with words of doubt; as did Moses, [when he] said (Numbers 11:22), "If the flocks and cattle be slaughtered for them, etc." And the Lord strengthened him – meaning Moses – in his mission, and said to him (11:23), "Is the Lord's hand short; now you will see, etc." And behold He similarly said to Abraham (Genesis 17:19), "Sarah your wife will certainly bear you a child, etc." And behold that the perfect ones are not of little faith, God forbid, in their investigating things until they are able to ascertain them as truth. And this is judged by ideas, not by statements. And this is shown with Sarah; as there is no doubt that her statement was the same as this statement of Abraham's. And there are countless other [examples] like these.

See my sons, I have revealed to you what the Lord has revealed of the secrets of our Torah to us; but He has not revealed it to all living beings. And you should know that I am giving to you for free that which I grasped in meditation and the persistence of my efforts during my days and my nights. So you should guard these matters for yourself, as they will save you from great enigmas and much strenuous exertion.

R. Yitschak Arama:

If we had come in the heels of the earlier scholars to distinguish between laughter and laughter, perhaps I would have found a little explanation for their words... However, in my opinion, there is no reason to force all of this. Rather the verses should be understood like their simple meaning. And in this matter a small trace of a sin and lack of faith was found with him (Abraham), peace be upon him; in the [same] manner as when our teacher Moses said (Numbers 11:22), "If the flocks and cattle be slaughtered for them, etc." According to the opinion of midrashic statements, [God] should have rebuked him to his face, except that that day was the day of a happy pronouncement, and not a day of rebuke and the reminding of sin. [Similarly,] on [this day,] the great commandment of circumcision was given to [Abraham] and to his sons in joy... And something similar to this happened on the day of the giving of the Torah... Likewise is the matter here with Sarah; and the Holy One, blessed be He, did not want to sadden him with words of rebuke 'on his wedding day.' So He held it for the third day after his circumcision, the day that Sarah was remembered. For it was revealed in front of Him that the occurrence of [Abraham] was the same as what would also happen with Sarah. And it was enough to rebuke [him] then, by [his] understanding that which [God] rebuked her through him, as it is stated (Genesis 18:13-14), "And the Lord said to Abraham, 'Why is this that Sarah laughed... Is anything wondrous for the Lord?'" Were it not for this (to rebuke Abraham as well), why did He not rebuke her to her face, between Him and her. Is her rebuke in front of her husband not more disgraceful than that which they said that He was careful [to avoid,] by changing [Sarah's] words because of the ways of peace (Yevamot 65b)? ..."And you shall call his name, Yitschak (he shall laugh)" (Genesis 17:19), in commemoration of your having laughed about it, in that it was such a wondrous thing in your eyes – and that was the beginning of the rebuke!