Where Did the Donkey Go?

As Avraham prepared to go to Akeidas Yitzchok the Torah tells us ויחבוש את חמורו, he saddled his donkey. Later, as he saw the place that was designated by Hashem for the Akeidah, he tells the two lads who were with them שבו לכם פה עם החמור, "Remain here with the donkey." However, at the end of the story, when Avraham returns from the Akeidah, it says וישב אברהם אל נעריו, ויקומו וישבו, "And Avraham returned to his lads and they arose and returned."

Why doesn't it mention that he returned to the lads and the donkey? Why was the donkey so significant that the Torah mentioned it twice? And if it was so significant why was it then ignored at the end of the story?

The Akeidah was the final of Avraham's Ten Tests. The challenges provided by the tests afforded opportunities to Avraham to transcend the person he was at birth and become the spiritual progenitor of the Jewish Nation. Spiritual Laws of Inertia, the comfort we find in remaining as we are and fear of change, frequently prevent us from such transcendence. Even if we are cognizant of the need and benefit of such change we allow ourselves to be dragged down and remain as we are.

According to the Mahara"l the donkey, the חמור, shares the same root as the word חומר, physical substance.  The sluggish, plodding donkey symbolizes that which connects us to our baser selves and prevents us from transcending into more spiritual people.

I would therefore suggest that when Avraham began his trip to the Akeidah by saddling his donkey, he was  at the point, after passing nine tests already, where he had completely identified and had dominion over those aspects of his self that were preventing his total transcendence. As he approached the place of the Akeidah he left the donkey behind. He was finally able to separate himself from those factors and move ahead.

The transcendence was actualized by his performance at the Akeidah. As such when he returned there was no donkey left to return to. He had gotten rid of it entirely.