Sometimes Messenger of Allah ﷺ would not fast (for so many days) that we thought that he would not fast that month and he sometimes used to fast (for so many days) that we thought he would not leave fasting throughout that month and (as regards his prayer and sleep at night), if you wanted to see him praying at night, you could see him praying and if you wanted to see him sleeping, you could see him sleeping.  

أَنَّهُ سَمِعَ أَنَسًا ؓ يَقُولُ كَانَ رَسُولُ اللَّهِ ﷺ يُفْطِرُ مِنَ الشَّهْرِ حَتَّى نَظُنَّ أَنْ لاَ يَصُومَ مِنْهُ وَيَصُومُ حَتَّى نَظُنَّ أَنْ لاَ يُفْطِرَ مِنْهُ شَيْئًا وَكَانَ لاَ تَشَاءُ أَنْ تَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلاَّ رَأَيْتَهُ وَلاَ نَائِمًا إِلاَّ رَأَيْتَهُ  

Anas bin Malik was asked about the Prophet's fasting and he said: "He would fast during a month until we thought that he did not want to abstain from fasting during any of it. And, he would not fast during a month until we thought that he did not want to fast during any of it. (There was no time) that I wanted to see if he was performing Salat during the night, except that I would see him praying, nor to see him sleeping, except that I would see him sleeping."  

عَنْ صَوْمِ النَّبِيِّ ﷺ قَالَ كَانَ يَصُومُ مِنَ الشَّهْرِ حَتَّى نَرَى أَنَّهُ لاَ يُرِيدُ أَنْ يُفْطِرَ مِنْهُ وَيُفْطِرُ حَتَّى نَرَى أَنَّهُ لاَ يُرِيدُ أَنْ يَصُومَ مِنْهُ شَيْئًا وَكُنْتَ لاَ تَشَاءُ أَنْ تَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلاَّ رَأَيْتَهُ مُصَلِّيًا وَلاَ نَائِمًا إِلاَّ رَأَيْتَهُ نَائِمًا  

Anas bin Malik was asked about the Prophet's fasting and he said: "He would fast during a month until we thought that he did not want to abstain from fasting during any of it. And, he would not fast during a month until we thought that he did not want to fast during any of it. (There was no time) that I wanted to see if he was performing Salat during the night, except that I would see him praying, nor to see him sleeping, except that I would see him sleeping." (Using translation from Tirmidhī 769)   

عَنْ صَلَاةِ النَّبِيِّ ﷺ وَصَوْمِهِ تَطَوُّعًا قَالَ كَانَ يَصُومُ مِنَ الشَّهْرِ حَتَّى نَقُولَ مَا يُرِيدُ أَنْ يُفْطِرَ مِنْهُ شَيْئًا وَيُفْطِرُ حَتَّى نَقُولَ مَا يُرِيدُ أَنْ يَصُومَ مِنْهُ شَيْئًا وَمَا كُنَّا نَشَاءُ أَنْ نَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلَّا رَأَيْنَاهُ وَلَا نَرَاهُ نَائِمًا إِلَّا رَأَيْنَاهُ  

Anas bin Malik was asked about the Prophet's fasting and he said: "He would fast during a month until we thought that he did not want to abstain from fasting during any of it. And, he would not fast during a month until we thought that he did not want to fast during any of it. (There was no time) that I wanted to see if he was performing Salat during the night, except that I would see him praying, nor to see him sleeping, except that I would see him sleeping." (Using translation from Tirmidhī 769)  

عَنْ صَوْمِ النَّبِيِّ ﷺ قَالَ «كَانَ يَصُومُ مِنَ الشَّهْرِ حَتَّى نَرَى أَنَّهُ لَا يُرِيدُ أَنْ يُفْطِرَ مِنْهُ شَيْئًا وَيُفْطِرُ مِنَ الشَّهْرِ حَتَّى نَرَى أَنَّهُ لَا يُرِيدُ أَنْ يَصُومَ مِنْهُ شَيْئًا وَكُنْتَ لَا تَشَاءُ أَنْ تَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلَّا رَأَيْتَهُ مُصَلِّيًا وَلَا نَائِمًا إِلَّا رَأَيْتَهُ»  

Anas bin Malik was asked about the Prophet's fasting and he said: "He would fast during a month until we thought that he did not want to abstain from fasting during any of it. And, he would not fast during a month until we thought that he did not want to fast during any of it. (There was no time) that I wanted to see if he was performing Salat during the night, except that I would see him praying, nor to see him sleeping, except that I would see him sleeping." (Using translation from Tirmidhī 769)   

عَنْ صَلَاةِ النَّبِيِّ ﷺ وَصَوْمِهِ تَطَوُّعًا قَالَ كَانَ يَصُومُ مِنَ الشَّهْرِ حَتَّى نَقُولَ مَا يُرِيدُ أَنْ يُفْطِرَ مِنْهُ شَيْئًا وَيُفْطِرُ مِنَ الشَّهْرِ حَتَّى نَقُولَ مَا يُرِيدُ أَنْ يَصُومَ مِنْهُ شَيْئًا وَمَا كُنَّا نَشَاءُ أَنْ نَرَاهُ مِنَ اللَّيْلِ مُصَلِّيًا إِلَّا رَأَيْنَاهُ وَلَا نَرَاهُ نَائِمًا إِلَّا رَأَيْنَاهُ