It is narrated from Sayyiduna Sahl bin Hunayf (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever performs ablution and performs it well, then prays two rak'ahs in the Mosque of Quba, they become for him equal to an Umrah."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5540