FLEXIBILITY OF THE PROPHET, praise and peace be upon him H 1193 "Sometimes, the Messenger of Allah, praise and peace be upon him, did not fast during a month until we thought he was not going to fast at all during that month. At other times he would fast continuously and we thought he would not stop fasting at all during that month. If one wanted to see him offering his prayers during the night one could do that or if one wished to see him sleep during the night he could do that also." R 1193 Bukhari with a chain up to Anas who related this.
1170- وعن أنس رضي الله عنه ، قَالَ : كَانَ رسولُ اللهِ صلى الله عليه وآله وسلم يُفْطِرُ مِنَ الشَّهْرِ حَتَّى نَظُنَّ أنْ لاَ يَصُومَ مِنْهُ ، وَيَصُومُ حَتَّى نَظُنَّ أنْ لاَ يُفْطِرَ مِنْهُ شَيْئاً ، وَكَانَ لاَ تَشَاءُ أنْ تَرَاهُ مِنَ اللَّيلِ مُصَلِّياً إِلاَّ رَأيْتَهُ ، وَلاَ نَائِماً إِلاَّ رَأيْتَهُ . رواه البخاري .