Narrated 'Aisha:

Whenever Allah's Messenger () ordered the Muslims to do something, he used to order them deeds which were easy for them to do, (according to their strength and endurance). They said, "O Allah's Messenger ()! We are not like you. Allah has forgiven your past and future sins." So Allah's Apostle became angry and it was apparent on his face. He said, "I am the most Allah fearing, and know Allah better than all of you do."

حَدَّثَنَا مُحَمَّدُ بْنُ سَلاَمٍ، قَالَ أَخْبَرَنَا عَبْدَةُ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا أَمَرَهُمْ أَمَرَهُمْ مِنَ الأَعْمَالِ بِمَا يُطِيقُونَ قَالُوا إِنَّا لَسْنَا كَهَيْئَتِكَ يَا رَسُولَ اللَّهِ، إِنَّ اللَّهَ قَدْ غَفَرَ لَكَ مَا تَقَدَّمَ مِنْ ذَنْبِكَ وَمَا تَأَخَّرَ‏.‏ فَيَغْضَبُ حَتَّى يُعْرَفَ الْغَضَبُ فِي وَجْهِهِ ثُمَّ يَقُولُ ‏ "‏ إِنَّ أَتْقَاكُمْ وَأَعْلَمَكُمْ بِاللَّهِ أَنَا ‏"‏‏.‏

Reference	: Sahih al-Bukhari 20
In-book reference	: Book 2, Hadith 13