When we look into Rashi we see it was the same donkey that Avraham had used was now used by Moshe. It will also be used by Moshiach.
Pirkei dRebbi Eliezer also explains that this donkey was born to the donkey that was created on the first friday , the one that spoke to Bilam.
Now may be a good time for a gem of Torah study.
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