1 Kings 1:33
The king also said unto them, Take with you the servants of your lord, and cause Solomon my son to ride upon mine own mule, and bring him down to Gihon: The king also said unto them, Take with you the servants of your lord, and cause Solomon my son to ride upon mine own mule, and bring him down to Gihon:
The command belongs to David's response to Adonijah's rebellion, given after David was reminded that God had directed Solomon to succeed him, upon which David yielded the throne to Solomon. David decisively ordered his servants to take Solomon down to Gihon, causing him to ride upon David's own mule, as part of publicly installing Solomon as king. Having Solomon ride the king's own mule publicly marked him as David's chosen successor.
Solomon was then immediately anointed and proclaimed king. This prompt action prevented Adonijah's rebellion from gaining control and thwarted it.