Whoso are deeply assimilated in the Oneness of Allah and have reached the state of complete self-effacement, they have fully recognized the Prophethood of Prophet Muhammad, (May Allah’s blessings be on him!), as the final apostle of Allah and submitted themselves totally to the orders of Allah and the Prophet. Thus they are de facto Muslims. They have done it out of love. In recognition thereof, Allah has absolved them of all earthly affiliations and impurities, more so because they are assimilated in the Oneness of Allah. This is what Abdul Latif says.
زانکہ در الاست اُو از لا گذشت
ہرکہ در اِلاست او فانی نہ گشت
(Roomi)
He has passed from the annihilation to the abiding existence and he who exists in the abiding existence is not mortal.
Note: (1) The last Prophet is the first Prophet also, as he satisfies completely the requirements of all people. He is the last Prophet as there shall be no Prophet after him. In fact no Prophet shall be needed after him. Accordingly he is the Prophet of the past, of the present and of the future at the same time. He is the Prophet complete in all respects. He combines all earlier prophets in himself.
(2) The person who reaches the stage of self-annihilation does not become a part of Allah or merge in Him. Allah is much too Holy for such association or absorption. The person maintains his individual entity, though he recedes into oblivision.
The highest is the position of those who attend to the Divine world and sink themselves in its ever lasting lights and in the branches of the Divine gnosis (knowledge) and are sometimes referred to in the Quran as the ‘foremost’. The Quran says: “the foremost in the race; these are they who would be brought nigh. (vide verses No.10-11 Al-Wakiah). (lmam Razi-lbn Al-lkhlaq).

Slain by Oneness they are cut into two halves,
By their belief that there is no God but Him.
Having accepted the Prophethood and Muhammad they immersed in it,
Lateef says, the lovers took this path,
God wished them when they became one with Oneness.