It's the hardest passage of all, one that seems to defy understanding.

Avraham and Sarah have waited years for a child.

God has promised them repeatedly that they would have many descendants,

as many as the stars of the sky, the dust of the earth.

The sand grains on the seashore. They wait. No child comes. Sarai in despair suggests

that Avram should have a child by her handmaid Agha. He does. Ishmael is born.

Yet God tells Avraham, this is not the one. By now Sarah is old, postmenopausal, unable by any natural means to have a child.

Angels come and again, they promise a child. Sarah laughs. But a year later, Yitzhak is born.

Sarah's joy is almost heartbreaking. Sarah said God has brought laughter, and everyone who hears about this will laugh with me.

And she added, who would have said to Avran that Sarah would nurse children?

Yet I have born him as son in his old age.

And then come the fateful words.

Then God said, take your son, your only son, Yitzhak, whom you love, and go to the region of Moriah.

Sacrifice him there as a burnt offering on one of the mountains I'll tell you about.

The rest of the story is familiar.

Abraham takes Yitzchak together, they journey for three days to the mountain.

Aram builds an altar, gathers wood, binds his son, and lifts the knife.

And at that moment, the angel of the Lord called out to him from heaven.

Avraham, Avraham, here I am, he replied.

Don't lay a hand on the boys, says the angel.

Don't do anything to him. Now I know that you'll fear God,

because you have not withheld from me, your son, your only son. The trial is over. It's the

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