Nasai

(1) From this narration, the reality of the matter becomes clear that Umar radi Allahu anhu considered it legally permissible, but due to the aforementioned reason, he did not regard Hajj Tamattu' as preferable. This was an ijtihadi (independent juristic) error on his part; however, the correct view is that Hajj Tamattu' is superior. And Allah knows best.

(2) "The Prophet sallallahu alayhi wa sallam did this." That is, he gave this command; otherwise, he himself did not become halal (exit the state of ihram). Or, in the literal sense, he performed tamattu'. And in this sense, Umar radi Allahu anhu also did not dislike tamattu' (qiran).

(3) "Under the trees of the pilu (Salvadora)..." In those days, these trees must have been common there, hence they were mentioned incidentally.

Hadith Commentary: Benefits and Issues:

➊
From the incident of Abu Musa al-Ash‘ari (radi Allahu anhu), it is established that, out of necessity, one may suspend one’s ihram upon the ihram of another respected person whom one intends to follow, and the specification of this ambiguity can later be determined by joining that person.

➋
After donning the ihram at the miqat, it cannot be ended without performing ‘umrah; however, in case of necessity or an impediment, it is permissible to change the state of ihram. Abu Musa (radi Allahu anhu) had suspended his ihram upon the Messenger of Allah (sallallahu alayhi wa sallam). The Prophet (sallallahu alayhi wa sallam) was performing qiran, because, due to bringing the sacrificial animal (hady) with him, he (sallallahu alayhi wa sallam) could not exit the state of ihram before completing the Hajj. But Abu Musa (radi Allahu anhu) did not have a hady, so the Prophet (sallallahu alayhi wa sallam) instructed him to perform tamattu‘ Hajj; thus, he performed ‘umrah and became lawful (halal).

➌
According to the terminology of the Qur’an, both tamattu‘ Hajj and qiran Hajj (since both are performed in the same journey) are called tamattu‘ Hajj. That is why ‘Umar (radi Allahu anhu) said: “I know very well that the Messenger of Allah (sallallahu alayhi wa sallam) and his companions performed tamattu‘ Hajj.” However, he used to prohibit tamattu‘ Hajj due to a certain expediency and wisdom, not because he denied its permissibility. The details have already been mentioned under Hadith number 145.

Benefits and Issues:
➊
This narration also establishes that Umar (radi Allahu anhu) did not consider Hajj al-Tamattu‘ to be legally prohibited.

➋
The Messenger of Allah (sallallahu alayhi wa sallam) performed Hajj al-Qiran.
When Umar (radi Allahu anhu) said that the Messenger of Allah (sallallahu alayhi wa sallam) performed Tamattu‘, by this he intended the literal meaning of Tamattu‘—that is, obtaining the benefit of both Hajj and ‘Umrah in a single journey.
Or, it means that the noble Companions (radi Allahu anhum) performed Tamattu‘ by the command of the Messenger of Allah (sallallahu alayhi wa sallam), and considering his command to be equivalent to action, this statement was made.