Sahih Muslim Introduction 12
Muhammad bin ul-Muthannā narrated to us, he said I heard Abd ar-Rahman bin Mahdī saying:
‘A man cannot be an Imām whose example is followed until he withholds from some of what he hears’.
وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ سَمِعْتُ عَبْدَ الرَّحْمَنِ بْنَ مَهْدِيٍّ، يَقُولُ لاَ يَكُونُ الرَّجُلُ إِمَامًا يُقْتَدَى بِهِ حَتَّى يُمْسِكَ عَنْ بَعْضِ مَا سَمِعَ ‏.‏