Ibn Majah

Commentary:
(1)
This narration is weak in its chain of transmission; however, based on corroborating evidence, it is authentic. But the word (khassatan) mentioned in this narration is not authentic. For details, see the verification and referencing of this very hadith.

(2)
The incident of Umar radi Allahu anhu accepting Islam occurred in the 6th year of Prophethood, that is, seven years before the Hijrah. See: (Al-Raheeq Al-Makhtum, by Maulana Safiur Rahman Mubarakpuri, p. 145).
At that time, Aisha radi Allahu anha would have been approximately one year old. Therefore, if this supplication is related to Umar radi Allahu anhu accepting Islam, it is evident that Aisha radi Allahu anha did not hear it directly from the Messenger of Allah sallallahu alayhi wa sallam, but rather heard this hadith from another companion.
However, on this basis, this hadith cannot be declared weak, because in such a case it will be counted among the mursal narrations of the companions (mursalat al-sahabah), which are considered authentic by the hadith scholars (muhaddithun).
But it is also possible that this supplication was not for Umar radi Allahu anhu accepting Islam.
And the Noble Prophet sallallahu alayhi wa sallam made this supplication at a time when Aisha radi Allahu anha had already become his wife, and thus she heard it directly from him sallallahu alayhi wa sallam.
In this case, what is meant are the outstanding achievements in the later life of Umar radi Allahu anhu, which include the defeat of powerful disbelieving empires such as Rome and Persia, and the astonishing expansion of the Islamic state.

(3)
The supplication of the Noble Prophet sallallahu alayhi wa sallam for Umar radi Allahu anhu is a clear proof of his virtue.