Why did Ali (a.s) order to be buried in secret?

It is said that Ali (a.s) asked his friends and family to bury him secretly. His burial was revealed only later during the Abbasid caliphate by Imam Ja'far al-Sadiq (a.s), his descendant and the sixth Shia Imam. * **Why did he order to be buried in secret?** **Ref:** *Al-Shaykh Al-Mufid (1986). Kitab Al-Irshad: The Book of Guidance into the Lives of the Twelve Imams. Routledge Kegan & Paul. ISBN 978-0-7103-0151-2. *