Mishkat al-Masabih 272
‘Abdallah [b. Mas'ud] said:
If any of you people knows anything he should
make it known, but if anyone does not know he should say that God
knows best, for saying this when one does not know is a part of knowledge. God said to His prophet, “Say, I do not ask you for any reward
for it, and I am not a pretender.”* (Bukhari and Muslim.)
*Qur’an, xxxviii, 86.
وَعَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ قَالَ: يَا أَيُّهَا النَّاسُ مَنْ عَلِمَ شَيْئًا فَلْيَقُلْ بِهِ وَمَنْ لَمْ يَعْلَمْ فَلْيَقُلِ اللَّهُ أعلم فَإِن من الْعلم أَن يَقُول لِمَا لَا تَعْلَمُ اللَّهُ أَعْلَمُ. قَالَ اللَّهُ تَعَالَى لِنَبِيِّهِ (قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ وَمَا أَنا من المتكلفين)