I asked or someone asked the Prophet ﷺ about perpetual fasting. He replied: You have a duty to your family. Fast during Ramadan and the following month, and every Wednesday and Thursday. You will then have observed a perpetual fast.  

سَأَلْتُ أَوْ سُئِلَ النَّبِيُّ ﷺ عَنْ صِيَامِ الدَّهْرِ فَقَالَ إِنَّ لأَهْلِكَ عَلَيْكَ حَقًّا صُمْ رَمَضَانَ وَالَّذِي يَلِيهِ وَكُلَّ أَرْبِعَاءَ وَخَمِيسٍ فَإِذَا أَنْتَ قَدْ صُمْتَ الدَّهْرَ  

"I asked - or; the Prophet was asked - about fasting daily. So he said: 'Your family has a right over you.' Then he said: 'Fast Ramadan and that which is after it, and every Wednesday and Thursday. If you do that, then you will have fasted daily, as well as broken (the fast).'"  

سَأَلْتُ أَوْ سُئِلَ رَسُولُ اللَّهِ ﷺ عَنْ صِيَامِ الدَّهْرِ فَقَالَ إِنَّ لأَهْلِكَ عَلَيْكَ حَقًّا صُمْ رَمَضَانَ وَالَّذِي يَلِيهِ وَكُلَّ أَرْبِعَاءٍ وَخَمِيسٍ فَإِذًا أَنْتَ قَدْ صُمْتَ الدَّهْرَ وَأَفْطَرْتَ وَفِي الْبَابِ عَنْ عَائِشَةَ  

[Machine] I asked the Messenger of Allah ﷺ about fasting three times. He said, "Fast the month of Ramadan and the month after it, and fast on Wednesdays and Thursdays, then you will have fasted the whole year and have broken the fast."  

سَأَلْتُ رَسُولَ اللهِ ﷺ عَنِ الصِّيَامِ ثَلَاثًا قَالَ «صُمْ شَهْرَ رَمَضَانَ وَالَّذِي يَلِيهِ وَيَوْمَ الْأَرْبِعَاءِ وَالْخَمِيسِ فَإِذًا أَنْتَ قَدْ صُمْتَ الدَّهْرَ وَأَفْطَرْتَ»  

"أَمَا لأهْلِكَ حَقٌّ؟ صُمْ رمضانَ والذي يَلِيه، وَكلَّ يَوْمٍ أَرْبِعَاءَ وخميسٍ، فإِذا أنْتَ قَدْ صُمْتَ الدهرَ".  

"صُمْ رَمَضَانَ وَالَّذِى يَلِيهِ، وَكُلَّ أَرْبَعَاءَ وَخَميسٍ، فَإِذَا أَنْتَ صُمْتَ الدَّهْرَ كلَّهُ وَأَفْطَرْتَ".