Sahih Muslim , Book 15, Hadith 589 (In-Book) ⓘ
This hadith has been narrated on the authority of Zuhri (but with this change of words) that he (Allah's Apostle) said: " Undertake journey to three mosques."
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ الأَعْلَى، عَنْ مَعْمَرٍ، عَنِ الزُّهْرِيِّ، بِهَذَا الإِسْنَادِ غَيْرَ أَنَّهُ قَالَ " تُشَدُّ الرِّحَالُ إِلَى ثَلاَثَةِ مَسَاجِدَ " .
also referenced under: Hadith 1397 (Reference) & Book 7, Hadith 3219 (USC-MSA)