Riding on a Person's Neck
Scholars have said that seeing oneself riding on a person's neck may indicate the approach of one's death, and that the person being ridden will carry the dreamer's funeral. It has also been said that it points to undertaking a difficult matter; if the dreamer falls from that person's neck, the matter they sought might not be completed.
Per Ibn Sirin's Muntakhab al-Kalam fi Tafsir al-Ahlam