Sahih al-Bukhari 7178
Narrated Muhammad bin Zaid bin `Abdullah bin `Umar:
Some people said to Ibn `Umar, "When we enter upon our ruler(s) we say in their praise what is 
contrary to what we say when we leave them." Ibn `Umar said, "We used to consider this as 
hypocrisy."
حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا عَاصِمُ بْنُ مُحَمَّدِ بْنِ زَيْدِ بْنِ عَبْدِ اللَّهِ بْنِ عُمَرَ، عَنْ أَبِيهِ، قَالَ أُنَاسٌ لاِبْنِ عُمَرَ إِنَّا نَدْخُلُ عَلَى سُلْطَانِنَا فَنَقُولُ لَهُمْ خِلاَفَ مَا نَتَكَلَّمُ إِذَا خَرَجْنَا مِنْ عِنْدِهِمْ قَالَ كُنَّا نَعُدُّهَا نِفَاقًا‏.‏