[Well of al-‘Ihn]: with a kasra on the letter ‘ayn (unpointed), a sukun on the ha, and a nun. It is the fifth prophetic well.
It is one of the so-called "prophetic wells." The Messenger of Allah ﷺ spat water into this well, blessed it, and performed his ablutions there.
It is also called al-Yusayra (from yusr, "ease," as opposed to ‘usr, "hardship").
The historian al-Samhūdī said regarding it: "Upon reflection, it seems to me that the well of al-‘Ihn is the same well known as al-Yasīra. It is a well to which the Prophet ﷺ went, where he performed his ablutions and spat into it. The original name of the well was ‘Usra (difficulty), and the Prophet ﷺ named it al-Yusīra (the easy one)." (Paraphrased.)
Al-Samhūdī also reports from Sa‘īd b. ‘Amr: "The Messenger of Allah ﷺ came to the Banū Umayya b. Zayd and stopped at a well belonging to them. He asked, 'What is it called?' They replied, '‘Asīra.' He said, 'No, rather it is called al-Yasīra.' Then he spat into it and blessed it."
Ibn Shabbah reports, from Muḥammad b. Ḥāritha al-Anṣārī, from his father, that the Prophet ﷺ gave the name "al-Yasīra" to the well of the Anṣār clan of Banū Umayya, that he blessed this well, performed his ablutions there, and spat into it (See: Tārīkh al-Madīnah, 1/161).
The companion Abū Salama b. ‘Abd al-Asad was washed upon his death with the water of this well. Abū Salama was the foster-brother (through nursing) and cousin of the Prophet ﷺ (son of his aunt Barra bint ‘Abd al-Muṭṭalib). He was also the husband of Umm Salama before the Messenger of Allah ﷺ married her.
Ibn Sa‘d reports in al-Ṭabaqāt:
From ‘Umar b. Abī Salama: Abū Salama took part in Badr and Uḥud. The one who wounded him at Uḥud was Abū Usāma al-Jushamī, who shot him with a broad-headed arrow (mi‘bala) in the upper arm. Abū Salama spent a month treating it and appeared to have healed, but the wound had closed over a hidden ailment he did not suspect. The Messenger of Allah ﷺ then dispatched him, during the month of Muḥarram—in the thirty-fifth month after the Hijrah—at the head of an expedition against Banū Asad, to Qaṭan. Abū Salama spent about ten nights there before returning to Madinah. Upon his return, the wound reopened; he fell ill and died on the third of the month of Jumādā al-Ākhirah. He was washed with the water of al-Yasīra, the well of Banū Umayya b. Zayd located in al-‘Āliya. That was where he used to stay in Qubā’ since leaving that area. His body was washed between the two upright supports of the well. It was called al-‘Usra during the pre-Islamic era, and the Messenger of Allah ﷺ named it al-Yasīra. The body of Abū Salama was then carried from the quarter of Banū Umayya b. Zayd to be buried in the center of Madinah. ‘Umar b. Abī Salama said: "My mother Umm Salama then observed her waiting period (‘iddah) to its completion: four months and ten days."
Ibn Sa‘d, 3/240
