The manifestation of this duty is through the remembrance of Imam Mahdi (as) through the mention of his Fazael (merits, excellences or special qualities).
Proof for this is based on the general traditions that recommend the narration of the excellences of other Imams (as).
Imam Sadiq (as) said, It is the duty of a group of heavenly angels to look at two or three people who are discussing the merits of Ahle Bayt (as). One of the angels says, look at them! In spite of the fact that they are so few in number and in spite of having so many enemies they are still discussing the merits of Ahle Bayt (as). The other group of angels says, “That is Allah’s grace, He grants it to whom He pleases, and Allah is the Lord of mighty grace.” (Holy Quran chapter 62 verse 4) (Rauzat Al-Kafi volume 8 page 334)
Imam Baqir (as) said to one of his companions, Do you have secluded meetings and discuss among yourselves what you like? He replied, Yes, we indeed talk about the excellences of Ahle Bayt (as) in private. The Imam (as) said, I would like it very much to be present in those gatherings. By Allah, I like your fragrance and your souls. Indeed you are following the religion of the Allah and His angels, thus you help it through piety and effort. (Al Kafi, volume 2 page 187 tradition no. 5)
Imam Kazim (as) said, That which is most despicable for Satan and his group is mutual interaction of the believer for the sake of Allah. He said, when two believers meet and remember Allah and discuss the excellence of us, Ahle Bayt (as), Iblees scratches his face badly and then his soul screams due to the intensity of pain so much that the angels of the sky and the custodians of Paradise hear it and they curse him and no angel remains but that he curses him, thus the Satan becomes disgraced and helpless. (Al Kafi volume 2 page 188 tradition no. 7)
A perspective for supporting this point is the mention in traditions of responding to a good turn and to speak nicely of one who has done a favor to you. Like the tradition of Imam Sajjad (as) mentioned in Resalatul Huquq (Treatise of Rights). In the said tradition, the Imam explains the rights of one who has done a favor to us. He says, As for the right of one who has done a good turn to you it is that you be thankful to him and that you remember his favor and talk of him in good terms among the people and pray for him with all sincerity to the Almighty Allah; thus if you do this you have thanked him openly and privately and if one day you are capable you recompense his favor by doing a good turn to him.
For a believer who acknowledges the role that the Imam of the Time, Imam Mahdi (as) plays in his life that every aspect, every bounty flows from him, then speaking about the merits of Imam Mahdi (as) in society, calling people towards him becomes one of the foremost duties of an individual. It is our way of expressing thankfulness to him, remembering his favour. We can never repay the favour that the Imam (as) bestows upon us, but through this action we can make some small attempt towards it.
- Read More: Duties of Shiahs in Ghaybat