It is narrated from Hazrat Aisha that sometimes revelation would descend upon the Prophet (peace be upon him) while he was on his mount, and the animal would lower its neck to the ground.
Hadith Referenceمسند احمد / مسند النساء / 24868
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن لأجل عبدالرحمن