Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.070A.

Jabir reports that the Messenger of Allah said: “Prayer in the inviolable mosque [in Makkah] is like 100,000 prayers [elsewhere]. And prayers in my mosque [in Medinah] is like one thousand prayers [elsewhere]. And a prayer in Bait al-Maqdis [in Jerusalem] is like five hundred prayers [elsewhere]. This is related by alBaihaqi, and as-Sayuti says it is hasan.

Ahmad records that the Messenger of Allah said: “Offering salah in my mosque is better than one thousand prayers elsewhere, save for those offered in the inviolable mosque. And salah in the inviolable mosque is better than salah in my mosque by one hundred prayers.”

The Prophet said: “One should not undertake a journey, save to three mosques: the inviolable mosque [in Makkah], my mosque here [in Medinah], and Masjid al-Aqsa [in Jerusalem].” This is related by the group.