I asked ʿAisha "Did Allah s Apostle, use to choose some special days (for fasting)?" She replied, "No, but he used to be regular (constant) (in his service of worshipping). Who amongst you can endure what Messenger of Allah ﷺ used to endure?"  

عَنْ عَلْقَمَةَ قُلْتُ لِعَائِشَةَ ؓ هَلْ كَانَ رَسُولُ اللَّهِ ﷺ يَخْتَصُّ مِنَ الأَيَّامِ شَيْئًا قَالَتْ لاَ كَانَ عَمَلُهُ دِيمَةً وَأَيُّكُمْ يُطِيقُ مَا كَانَ رَسُولُ اللَّهِ ﷺ يُطِيقُ