Hazrat Fizza (SA) had the honour of taking part in the "Three Days Fast". Once, when Imam Hasan (AS) and Imam Husain (AS) fell sick, the Holy Prophet (S) suggested that Imam Ali (AS) make a vow (Nazr) to fast for three days when the children recovered.
When the children were better, Imam Ali (AS), Hazrat Fatimah (SA), Imam Hasan (AS), Imam Husain (AS) and Hazrat Fizza (SA) all fasted to fulfil the vow.
However, on each of the three days, when they sat to break their fast, a hungry person called at their door. The first said he was poor, the second said he was an orphan and the third said he was a freed captive. Each time, the big-hearted members of the house, including Bibi Fizza, gave away their food and broke their fast with water.
In praise of this selfless action Allah revealed the 76th Chapter of the Holy Qur'an. The incident is described as follows:
يُوفُونَ بِٱلنَّذۡرِ وَيَخَافُونَ يَوۡمً۬ا كَانَ شَرُّهُ ۥ مُسۡتَطِيرً۬ا (٧) وَيُطۡعِمُونَ ٱلطَّعَامَ عَلَىٰ حُبِّهِۦ مِسۡكِينً۬ا وَيَتِيمً۬ا وَأَسِيرًا (٨) إِنَّمَا نُطۡعِمُكُمۡ لِوَجۡهِ ٱللَّهِ لَا نُرِيدُ مِنكُمۡ جَزَآءً۬ وَلَا شُكُورًا (٩) إِنَّا نَخَافُ مِن رَّبِّنَا يَوۡمًا عَبُوسً۬ا قَمۡطَرِيرً۬ا (١٠) فَوَقَٮٰهُمُ ٱللَّهُ شَرَّ ذَٲلِكَ ٱلۡيَوۡمِ وَلَقَّٮٰهُمۡ نَضۡرَةً۬ وَسُرُورً۬ا (١١
"They who fulfil their vows, and fear the day, the woe of which stretches far and wide. And they give away food, out of love for Him, to the poor and the orphan and the captive, (saying), We feed you only for the sake of Allah, we do not want anything from you, not even thanks. Verily we fear from our Lord a stern day of distress. So Allah will guard them from the evil of that day and give them freshness and pleasure". (Surah Dahr - Insaan 76:7-11)