Donkeys are unclean in that they are not considered food for us by God. They are not unclean in the sense that they foul us ceremonially if we touch them. There is no such law in the Old Testament. So, like another poster here, I'm not sure I follow.
Thank you for this post. You have brought me to this point which has not yet (to my knowledge) been defined. There are the food laws which teach the acceptable and the unacceptable. The creature natures like the donkey, the oxen, the mule, the horse; all have been shown in real time life language. This is one of the things I consider; but the distinction of strength and purpose ended for me with which were used for food (as a disciple or Apostle). The strength of a horse had more to do with armies. But whether they were or were not acceptable as food, I do not have a verse or teaching on my mind to give an answer.
The use of the word 'filthy' in the thread pertains to the person (the creature nature). It is a query into how christians consider the person whom Jesus gave His life for. Early in my walk, I remember pointing my finger out at the world, saying, "See what evil there is; surely the end times are here!" These are the words of a hypocrite, and then this question I asked in the thread caused me to ponder just how much, how many I maligned in my walk. This is the reason for "Did Jesus ride a filthy creature"
The rest of the sentence gave a specific direction of the question, "triumphantly into Jerusalem"