Why did God test Abraham?
Abraham was tested through [the incident of] the offering up of his beloved son Isaac to prove his pious obedience and so make it known to the world, not to God... It says "Now I know" for "Now I have made known"--for certainly God was not ignorant [of this] previously.
What was so significant about Abraham's obedience?
Section VI
The Pilgrim’s family are shown some marvelous things.:
Then they took them, and had them to the Mount upon which Abraham our Father had offered up Isaac his Son, and shewed them the Altar, the Wood, the Fire, and the Knife, for they remain to be seen to this very day. When they had seen it, they held up their hands and blest themselves, and said, Oh what a man for love to his Master, and for denial to himself was Abraham…
The Pilgrim's family is then told:
Eve's Apple we have shew'd you,
Of that be you aware;
You have seen Jacob's Ladder too,
Upon which Angels are.
An Anchor you received have,
But let not these suffice,
Until with Abr'am you have gave
Your best a Sacrifice.