What are the compulsory deeds for people who are fasting?
What compulsory for the fasting ones are increasing their righteous deeds, and avoiding all prohibitions of religion. Whereas what they are requested to do are establishing their religious obligation and avoiding all forbidden things, for example by performing the five compulsory prayers in time in congregation, abandoning lies and gossips, frauds and usury, and all of the forbidden words or deeds. The Prophet -peace and prayer of Allah be upon him- had declared:
مَنْ لَمْ يَدَعْ قَوْلَ الزُّوْرِ وَالْعَمَلَ بِهِ وَالْجَهْلَ فَلَيْسَ للهِ حَاجَةٌ أَنْ يَدَعَ طَعَامَهُ وَشَرَابَهُ
“Whoever doesn’t abandon the lies and false deeds, and foolish act, then Allah has no need of him leaving his foods and drinks.” 
Fatwas regarding fasting, by Sheikh Ibn Uthaymeen , page 24.
 Narrated by Al Bukhari, in his work, “al-Adabul Mufrad” (6057)
Source of reference: The Actual Fatwas. Book 1. Published by Darul Haq.
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