رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 1764
The Book of the Prohibited actions
Prohibition of Extending Fast beyond one Day
عَنْ أَبِي هُرَيْرَةَ وَعَائِشَةَ رَضِيَ اللَّه عَنْهُمَا أَنَّ النَّبِيَّ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ نَهَى عَنِ الْوِصَالِ. ((مُتَّفَقٌ عَلَيْهِ)).
Abu Hurairah and 'Aishah (May Allah be pleased with them) said: The Prophet (ﷺ) prohibited observing continuous voluntary fasts beyond one day. [Al-Bukhari and Muslim].
Riyad as-Salihin, 1764