The entrance of Jesus into the Holy City, symbolic of dominating the lunar mind and achieving union of the Solar Christified Mental Body with the Spirit.  Lecture refers specifically to the Sephirah Netzach. Lecture quote:

"... the Bodhisattva, instead of identifying himself/herself with those two minds (Pharisees and Sadducees, believers and skeptics), what he does is to utilize his mind, he controls his mind, he works his Bodhichitta. This is why Jesus rides the animal when going to enter into Jerusalem, into the world of the mind, which is the world of Buddha, because in order to be enlightened you have to control completely your mind..."