Behind the mosque is the blessed Mazaar Shareef of Hadhrat Abu Ayyub al-Ansari or Khalid ibn Zayd ibn Kulayb. After Hijra, the Holy Prophet #ﷺ desired to stay at his maternal relatives home of Banu Najjar, thus Abu Ayyub's home was chosen.
Hadhrat Mirza Basheer Ahmad (ra) writes: "Abū Ayyūb (r) desired that the Holy Prophet (sa) stay on the top floor. However, taking into consideration the ease of those people who would come to visit, the Holy Prophet preferred the groundfloor and resided there. At nightfall, Abū Ayyūb and his wife could not sleep all night in the thought that the Holy Prophet was beneath them, and they were above him. In addition to this, it so happened that during the night a pale of water broke on the roof. In his fear, Abū Ayyūb quickly placed his quilt over the water to dry it, in order to prevent even a single droplet of water from seeping through to the ground floor. In the morning, he presented himself before the Holy Prophet, and implored the Holy Prophet to stay on the top floor. At first, the Holy Prophet hesitated, but upon witnessing the insistence of Abū Ayyūb, he agreed. The Holy Prophet stayed in this home for seven months, or according to Ibni Isḥāq, he remained here until the month of Ṣafar 2 A.H. In other words, the Holy Prophet remained here until the construction of Masjid-e-Nabawī, and the adjacent living-quarters of the Holy Prophet. Abū Ayyūb would present food to the Holy Prophet, and then, whatever would remain of it, he would eat himself. Due to his love and sincerity, he would eat from where the Holy Prophet had taken his food" - Life and Character of the Seal of Prophets, Volume 2, Page 11 - 4 years ago