[1] The hujja is an Islamic prophet or an Imam who possess a relationship with God that is greater than anyone else.
In Twelver shi'ism the title "hujja" is specifically applied to the Twelfth Imam who is believed to be in hiding and is attributed with the tradition of using Shi'i hadith to guide the religious community.
The second supposed proof an Imam is hujja is that "he is a channel of divine grace which comes to him inwardly from the suprasensible realm".
[3] Only those who are free from error can be considered divinely touched and therefore are hujja and entitled to the Imamate.
The fourth reason is said to be that God's grace keeps his creatures towards obedience and keeps them away from disobedience.