Sunan Ibn Majah - سنن ابن ماجه
4. The Book On The Mosques And The Congregations - كتاب المساجد والجماعات
3) Chapter: Where It Is Permissible To Build Mosque
It was narrated that Ibn 'Umar was asked about gardens in which excrement was thrown.:
He said: "If it has been watered several times, then perform prayer there," and he attributed that to the Prophet.
3) باب أَيْنَ يَجُوزُ بِنَاءُ الْمَسَاجِدِ
حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، حَدَّثَنَا عَمْرُو بْنُ عُثْمَانَ، حَدَّثَنَا مُوسَى بْنُ أَعْيَنَ، حَدَّثَنَا مُحَمَّدُ بْنُ إِسْحَاقَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، وَسُئِلَ، عَنِ الْحِيطَانِ، تُلْقَى فِيهَا الْعَذِرَاتُ فَقَالَ . يَرْفَعُهُ إِلَى النَّبِيِّ ـ صلى الله عليه وسلم ـ . " إِذَا سُقِيَتْ مِرَارًا فَصَلُّوا فِيهَا "