The Dai is the Maula of mumineen, whose kingdom is established on their hearts. He doesn’t need any physical or outer means to prove his leadership. Mumineen always flock towards him. This kingdom on the hearts and minds can never be claimed by force or coercion. It is a spontaneous and natural attraction and attachment between the Maula and his mumineen, because this relationship is based on love and love cannot be bought, or forced upon, or sought with any physical means. That is the reason why Muawyah, in spite of getting the caliphate from Imam HasanRA, poisoned him as he could not bear to see throngs of people gravitating towards Imam HasanRA out of love and obedience. This spiritual kingdom on the hearts and souls of mumineen is eternal and can never be usurped by the enemy.
And nobody can replace Maula on the throne of this kingdom but the true worthy, whom the preceding Maula selects and prepares. Nass is the declaration by the predecessor about his successor which is done implicitly and explicitly. In the beginning Rasuluallah SAW performed nass on Maulana Ali SA only among a select few of his family members. At the end of his life he proclaimed nass openly among 70,000 people who had gathered at Ghadeer e Khum.
Nass is not claimed or desired for or contested for. One doesn’t claim eligibility to the position of Dai. It is a bestowment of the predecessor on the one whom he finds the truly eligible amongst the people of his Dawat to take his place as the representative of the Imam. The mansoos always receives this bestowment with profound gratitude and humility, never ever claiming himself to be eligible or deserving. This humility is the hallmark of a true successor.
When Syedna Mohammed Burhanuddin RA performed nass on Syedna Mufaddal Saifuddin TUS in London, and the witnesses went to Syedna Saifuddin’s TUS house to inform him about the nass, his immediate reaction was to get down from the sofa onto the ground and plead that may Maula live forever and may I be fida’ on him. When Syedna Mohammed Burhanuddin RA performed nass on Syedna Mufaddal Saifuddin TUS in Raudat Tahera, in the presence of thousands of Mumineen, Syedna Mufaddal Saifuddin TUS, in gratitude and humility, said that he was deficient in his ilm, and amal, and prayed for the longevity of Syedna Mohammed Burhanuddin RA.