How could God tell a father to kill his own son?
The Torah tells you something in the first verse that Avraham is never told: "God tested Avraham." You read the whole story knowing it is a test. He walks for three days not knowing.
Rashi points to the wording of the command. God never says "slaughter him." He says "bring him up there as an offering." Rashi explains: God did not want Yitzchak slaughtered. He wanted him brought up the mountain. Once Avraham had brought him up, God told him to bring him down.
The Gemara goes further. Long afterward, the prophet Yirmiyahu attacked people who burned their children as offerings. He quoted God calling it something "I did not command, did not speak, and it never entered My mind." The Gemara reads that last phrase as about Yitzchak. The commentary printed under Rashi's name explains: though God commanded it, slaughtering him never entered His mind. It was only a test. The Torah counts burning children among the things God hates.
So what was it for? The Rambam says it shows how far love and awe of God can reach. A man who had longed for a child, and had one only after giving up hope, was ready to give that child up. And not because he feared punishment or hoped for a reward.
Rav Kook (the first Chief Rabbi of the Land of Israel, who died in 1935) looks at how it ends: "Do not reach out your hand against the boy." He reads this as God saying that the ban on shedding blood and a father's love for his son both stand exactly as they were, not moved by a hair. A father's love, he writes, itself comes straight from the love of God.
None of this makes the story comfortable, and the sources do not try to. The Midrash pictures Avraham reaching for the knife with tears running from his eyes into his son's. Even so, it says, his heart was glad to do the will of his Maker. What the story itself insists on is the line that stops it: "Do not do anything to him."
Bereishit 22:1-2, 22:12,Rashi on Bereishit 22:2,Taanit 4a, with the commentary printed as Rashi's, on Yirmiyahu 19:5,Devarim 12:31,Rambam, Guide for the Perplexed 3:24,Rav Kook, Olat Re'iyah, on the Akedah,Bereishit Rabbah 56:8Avraham argued with God to save Sodom. Why not to save his own son?
A few chapters earlier, God tells Avraham what is coming for Sodom, and Avraham pushes back hard: "Will the Judge of all the earth not do justice?" Here God asks for his son, and Avraham gets up early in the morning and goes. The Torah records no reply at all.
The Midrash says the silence was a choice. It has Avraham tell God afterward: "When You said 'take your son,' I had an answer. Yesterday You told me my descendants would come through Yitzchak. I did not say it. I held back my compassion to do what You wanted." The prayer that follows the Akedah in the siddur is built on that line.
Abarbanel (Don Yitzchak Abarbanel, a statesman and Torah commentator who was expelled from Spain in 1492) thinks God all but invited an argument. The command came as a request, with the word "please." And "your son, your only one, whom you love" spells out the reasons Avraham had to object or to pray, "more than he prayed for the people of Sodom." He did neither.
The Netziv (Rabbi Naftali Tzvi Yehuda Berlin, who led the Volozhin yeshiva in the 1800s) explains why that was the test. If a king told a close friend to do something like this, the friend would at least ask why. Avraham was that close to God. He had the nerve to plead at length for Sodom. But when the decree fell on his own son, "in a matter that touched himself, he said nothing." That, says the Netziv, is the first thing "now I know that you fear God" points to.
According to Rashi, the argument did come out in the end. Once the angel stopped him, Avraham asked: first You promised me descendants through Yitzchak, then You said take him, and now You say do not touch him? God answered: I never said to slaughter him. I said to bring him up. Now bring him down.
The Torah itself never explains the silence. These are readings of it, and the question is still a fair one.
Bereishit 18:25, 22:3,Bereishit Rabbah 56:10,Abarbanel on Bereishit 22,Netziv, Ha'amek Davar on Bereishit 22:12,Rashi on Bereishit 22:12Did Yitzchak know what was happening? Did he agree to it?
The Torah gives Yitzchak one line on the way up: "Here are the fire and the wood, but where is the lamb for the offering?" Avraham answers, "God will see to the lamb for the offering, my son." Then: "The two of them walked on together."
Rashi hears a second meaning in Avraham's answer. God will choose the lamb, and if there is no lamb, then "for the offering: my son." Yitzchak understood that he was going to be slaughtered, Rashi says, and the two of them still walked on "with the same heart."
The Midrash takes this all the way. Yitzchak was 37, it says, and nobody ties up a 37-year-old without his consent. It has him say: "Father, I am a young man, and I am afraid my body will shake from fear of the knife. Tie me well." In this reading the Akedah is as much Yitzchak's act as Avraham's. That is how the Mishnah Berurah speaks of it: "as Yitzchak gave himself up."
Ibn Ezra is not convinced. If 37 is a tradition that was handed down, he says, we accept it. But as reasoning it does not work. A grown man who volunteered would deserve twice his father's reward, and the Torah says nothing about Yitzchak's part. He also quotes a view that Yitzchak was five, and rejects it, because Yitzchak carried the wood.
His own view is that Yitzchak was about 13, and that his father bound him against his will. The proof is that Avraham kept the secret from him. Had he said "you are the offering," Yitzchak might have run.
So the commentators give you two Yitzchaks: a grown partner who asks to be tied tighter, and a boy who is not told. The Torah's few words leave room for both.
Bereishit 22:7-8,Rashi on Bereishit 22:8,Bereishit Rabbah 56:8,Mishnah Berurah 1:13,Ibn Ezra on Bereishit 22:5