What is the charity that is required to fulfil the expiation (fidyah)?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It is feeding six needy people. This is reported in the hadith of Kaʿb and is the view of those who say fasting is for three days.
2. It is feeding ten needy people. This is the view of those who require fasting for ten days.