Grape and Sadaqa

I heard Shaykh Hamza Y mention this in a lecture:

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 someone 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 Qur'an 99:7)