Sahih al-Bukhari · The Book of Holding Fast To The Qur’An and The Sunna

8- بَابُ مَا كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُسْأَلُ مِمَّا لَمْ يُنْزَلْ عَلَيْهِ الْوَحْيُ فَيَقُولُ: «لاَ أَدْرِي»:

(8) Chapter. Whenever the Prophet (p.b.u.h.) was asked about something regarding which no Verse was revealed, he would either say, "I do not know," or give no reply, but he never gave a verdict based on opinion or on Qiyas.

1 hadith · references 7309–7309