A man from the Companions of the Prophet ﷺ told me that the Messenger of Allah ﷺ prohibited cupping and perpetual fasting, but he had not made them unlawful showing mercy on his Companions. Thereupon he was asked: Messenger of Allah, you observe perpetual fast till dawn. He replied: I observe perpetual fast till dawn (for) my Lord gives me food and drink. (Using translation from Abū Dāʾūd 2374)   

عَنْ رَجُلٍ مِنْ أَصْحَابِ النَّبِيِّ ﷺ قَالَ نَهَى رَسُولُ اللهِ ﷺ عَنِ الْحِجَامَةِ لِلصَّائِمِ وَالْمُوَاصَلَةِ وَلَمْ يُحَرِّمْهَا عَلَى أَصْحَابِهِ فَقَالُوا يَا رَسُولَ اللهِ إِنَّكَ تُوَاصِلُ إِلَى السَّحَرِ قَالَ إِنْ أُوَاصِلُ إِلَى السَّحَرِ فَرَبِّي ﷻ يُطْعِمُنِي وَيَسْقِينِي