Praise be to Allah.
It is proven that al-waseelah, for which we pray for the Prophet (blessings and peace of Allah be upon him), is a level in Paradise that is for only one of the slaves of Allah, may He be exalted.
It was narrated from ‘Abdullah ibn ‘Amr ibn al-‘Aas that he heard the Prophet (blessings and peace of Allah be upon him) say: “When you hear the mu’adhdhin, say what he says, then send blessings upon me, for whoever sends blessing upon me once, Allah will send blessings upon him tenfold. Then ask Allah to grant me al-waseelah, for it is a station in Paradise which only one of the slaves of Allah will attain, and I hope that I will be the one. Whoever asks for al-waseelah for me, intercession will be permissible for him.” Narrated by Muslim (384).
This hadith indicates that only one of the prophets, and no more, will be entitled to the level of al-waseelah or deserve it.
There is nothing in the wording of the hadith to indicate that the Prophet who deserves it will be on his own there, because being alone is contrary to the joy and pleasure of Paradise, and the religious texts indicate that every believer in every level of Paradise will have his wives and servants with him, to make his joy and pleasure in Paradise complete.
Therefore it is quite reasonable to think that when the Prophet (blessings and peace of Allah be upon him) attains the level of al-waseelah, which none of the other prophets (peace be upon him) will share with him, it is quite reasonable to think that his wives will join him, so that his honour and rejoicing in his status will be complete, as ‘Ammaar ibn Yaasir said of ‘Aa’ishah (may Allah be pleased with her): By Allah, she is the wife of your Prophet (blessings and peace of Allah be upon him) in this world and the hereafter. Narrated by al-Bukhaari (7100).
And the same applies to all the wives of the Prophet (blessings and peace of Allah be upon him), according to the consensus of the scholars.
Ibn Katheer (may Allah have mercy on him) said:
The scholars are definitively agreed that those of his wives whom the Messenger of Allah (blessings and peace of Allah be upon him) left behind when he died are not permissible for any man after him to marry, because they are his wives in this world and the hereafter, and they are the Mothers of the Believers."(Tafseer Ibn Katheer 6/455).
We say: That is reasonable and logical, and there is no cause for confusion in the first place.
But it is appropriate for us to refrain from taking a firm stance regarding such matters of the unseen concerning which we have no clear text, for the matter is entirely in the hand of Allah. However, we should affirm in very clear terms that al-waseelah is the position of the Prophet (blessings and peace of Allah be upon him) in the Hereafter, and no one else is entitled to it.
And Allah knows best.