If I see a fasting person eating or drinking forgetfully during the daytime of Ramadan, and I am certain that he is doing that forgetfully since he is a righteous person, should I remind him or let him eat or drink, since Allah has fed him and quenched his thirst? Does the same ruling apply to the voluntary fasting?
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Eating, drinking or consuming other substances that render fasting invalid during the daytime of Ramadan is an evil and it is permissible to neither approve it nor remain silent regarding it. Therefore, when one sees a fasting person eating or drinking during the daytime of Ramadan, he has to alert him, as it is a part of cooperation in righteousness and piety and a form of changing evil. The fact that a person is blameless for eating or drinking forgetfully does not absolve those who see him doing that of liability without alerting him.
Allah Knows best.