Vol. 01 page 18 ff. Yishmael’s Bris was rational, and that is a liability compared with Yitzchok’s super-rational bond. It is the basis of the Jewish people and that they are a miraculous people attached to Hashem higher than reason, from infancy.

Vol. 25 page 86 ff. Yitzchok’s Bris is superior not only to Yishmael’s but to Avrohom’s as well. Avrohom’s Bris was from higher than reason, but his 99 years of preparation cover this over, and the idea that it is entirely from Hashem is not obvious.

Vol. 10 page 49 ff. Avrohom’s life is divided into two: before and after the Bris. Before he was doing Judaism (like a brick), afterwards he was Jew, a representative of God on this earth (like a stone which is natural and not like a brick which is artificial).

Likutei Sichos vol. 20 page 73 ff. The Akaida is the last great act of Avrohom’s incredible life. Only at this point is the Mesiras Nefesh of Avrohom Avinu revealed to be totally sacrificial, giving credibility to all the sacrifices he’d made until this point.

Likutei Sichos vol. 35 page 76-81. After all is said and done and Avrohom shows infinite loyalty to Hashem, he begins protesting. In this Sichha the Rebbe shows (in Rashi’s view at least), that Avrohom was never questioning God, but the fact that maybe Hashem thought he was somehow unworthy of giving of himself to…

Likutei Sichos vol. 01 page 31-4. Sara (the Zohar says) is the body and Avrohom is the Soul, yet, Avrohom 1) listens to her 2) mourns for her, as she is the purpose.

Likutei Sichos vol. 15 page 145 ff. After Sara passes away we see her life. Her life is about the Jewish people exclusively, while Avrohom is about all of humanity. This shows itself in each of the big events in this Parsha.

Likutei Sichos vol. 15 page 122 ff. Torah Ohr Toldos (beg.) This class combines a Sicha about Avrohom and the Torah Ohr (beginning of Parshas Toldos) that help enlighten what separated Avrohom from Yitzchok. Avrohom shone light and inspired from above, doing what appears in affect to be forcing Arabs to see things his way,…

Likutei Sichos vol. 30 page 122 ff. Yitzchok’s idea is digging wells. What water the wells give him is Hashem’s business. As a result his wells last. The three wells, built with different levels of dedication and sacrifice last for different lengths of time. The third which is through Bittul and Kabbalas Ol lasts forever.

Likutei Sichos vol. 30 page 103 ff. Yitzchok is even more like Avrohom, chesed, than is Avrohom himself because of the Bittul of Yitzchok.