Question 21: Some people believe that if a pilgrim is not able to visit Al-Masjid Al-Nabawee (the Prophet’s Mosque in Madeenah), their Hajj is incomplete. Is this true
Answer: Visiting Al-Masjid Al-Nabawee is a Sunnah (supererogatory act of worship following the example of the Prophet), not Waajib (obligatory). It is not connected with Hajj; it is a Sunnah to visit Al-Masjid Al-Nabawee at any time of the year, not only at the time of Hajj, according to the saying of the Prophet (peace be upon him): No journey should be undertaken except to three Masjids: Al-Masjid Al-Haram (the Sacred Mosque in Makkah), this Masjid of mine (the Prophet’s Mosque), and Al-Masjid Al-Aqsaa (the Aqsa Mosque in Jerusalem). (Agreed upon by Al-Bukhaaree and Muslim)… read more here.