Hadith 518300
Chapter 58: Sadaqa - كتاب الصدقة
وَحَدَّثَنِي عَنْ مَالِكٍ، قَالَ بَلَغَنِي أَنَّ مِسْكِينًا، اسْتَطْعَمَ عَائِشَةَ أُمَّ الْمُؤْمِنِينَ وَبَيْنَ يَدَيْهَا عِنَبٌ فَقَالَتْ لإِنْسَانٍ خُذْ حَبَّةً فَأَعْطِهِ إِيَّاهَا فَجَعَلَ يَنْظُرُ إِلَيْهَا وَيَعْجَبُ فَقَالَتْ عَائِشَةُ أَتَعْجَبُ كَمْ تَرَى فِي هَذِهِ الْحَبَّةِ مِنْ مِثْقَالِ ذَرَّةٍ
Yahya related to me that Malik said, "I heard that a beggar asked for food from A'isha, umm al-muminin, while she had some grapes. She told some one to take him one grape. He began to look in amazement. A'isha said, 'Are you amazed? How many atoms' weights do you see in this grape?' " (referring to Sura 99 ayat 7).
Reference Muwatta Malik 518300
USC-MSA web (English) reference : Book 58, Hadith 6