The Book of Mosques and Places of Prayer
وَحَدَّثَنَاهُ يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا فُضَيْلُ بْنُ عِيَاضٍ، عَنْ مَنْصُورٍ، بِهَذَا الإِسْنَادِ وَقَالَ " فَلْيَتَحَرَّ الَّذِي يُرَى أَنَّهُ الصَّوَابُ " .This hadith has been reported by Mansur with the same chain of transwitters and he said:" He should aim at what is according to him correct
From Sahih Muslim, whose reports the scholars accept as authentic.