This is not something restricted to the state of ihram; it is prescribed whenever a need arises, and the same ruling applies to Friday and the two Eids.

I add: the bath over which Ibn ʿAbbās and al-Miswar disputed was not the bath taken in preparation for ihram, but rather one performed while already in ihram—that is exactly what Abū Ayyūb did.

Chapter: Converting Hajj into ʿUmrah

First ḥadith
Jabir ibn ʿAbd Allah reported: The Prophet ﷺ and his Companions entered ihram with the intention of Hajj, and none of them had sacrificial animals except the Prophet ﷺ and Ṭalḥah.

ʿAlī arrived from Yemen and said, “I have assumed ihram for whatever the Prophet ﷺ has assumed it for.” The Prophet ﷺ then ordered his Companions to change their intention to ʿUmrah: they were to circumambulate the House, shorten their hair, and leave ihram—except for anyone who had brought a sacrificial animal.

They said, “Shall we go to Mina while one of us still has his private part dripping (from recent marital relations)?”

When this reached the Prophet ﷺ he said, “Had I known beforehand what I know now, I would not have driven the sacrificial animals; were it not that I have them with me, I too would have left ihram.”

ʿĀʾishah began menstruating, so she performed all the rites except tawāf of the House. When she became pure and completed her tawāf she said, “Messenger of Allah, you will return with both Hajj and ʿUmrah while I return with only Hajj!” He therefore instructed ʿAbd al-Raḥmān ibn Abī Bakr to take her to Tanʿīm, and she performed an ʿUmrah after the Hajj.

Overall meaning
Jabir ibn ʿAbd Allah (may Allah be pleased with him) relates that the Prophet ﷺ and his Companions assumed ihram for Hajj, and only the Prophet ﷺ and Ṭalḥah ibn ʿUbayd Allah drove sacrificial animals. ʿAlī ibn Abī Ṭālib was in Yemen; when he arrived, he entered ihram and attached his intention to that of the Prophet ﷺ.

When they reached Mecca, the Prophet ﷺ instructed them to dissolve their ihram for Hajj and convert it into ʿUmrah: they were to perform tawāf and saʿy for ʿUmrah, then shorten their hair and leave ihram completely. This applied to those who had not brought sacrificial animals.

Those who had brought them—including the Prophet ﷺ—remained in ihram even after their tawāf and saʿy.

Those ordered to switch from Hajj to ʿUmrah, astonished and somewhat uneasy, said, “How can we go to Mina in the state of Hajj after we will have only just resumed relations with our wives?”

When their words and their sense of gravity over the matter reached the Prophet ﷺ, he