After the Imamah itself and his concealment are established...
After the Imamah itself and his concealment are established, certainty of the existence of grace and presence of a benefit in his existence is necessary, since if the appointment of an Imam who has been commanded to go into concealment does not entail grace, it is futile and vain; and Allah is far above vain and futile actions. Therefore, the appointment of a concealed Imam by Allah certainly entails lutf (grace).
Granted, if we wish to establish both the necessity of appointment of an Imam and the Imamah of a concealed person through the principle of grace, the objection arises that it must first be known that the concealed Imam entails grace. Otherwise, without knowledge of its being grace, his Imamah will not be established.
It is worthy of mention that if the objection of the absence of grace with regard to the concealed Imam be valid, it is also applicable to an Imam who is not concealed, yet who is not able to act freely in affairs. His Imamah will be without grace for the same reason that the Imamah of the concealed Imam is regarded as being without grace. However, this objection has not been made with regard to the manifest Imam who is not able to freely act in the affairs and tasks pertaining to Imamah .
Similarly, it has not been made regarding a prophet who, due to circumstances, is unable to guide others or whose guidance is not effective, or a prophet whose mission was general, but opponents and adversaries prevented his message from reaching the entire public, and it has not been denied that his prophecy entails grace.