What is the ruling on using a mobile phone in the mosque, especially WhatsApp?

The ruling on using a mobile phone in the mosque varies depending on its use. If it is used for an act of obedience, such as reading Qur'an, performing dhikr (remembrance of God), or listening to a lecture, then it is an act of obedience. If it is used for something permissible (mubah), then it is permissible. Similarly, the WhatsApp application: if it is used for sending something that is an act of obedience, then it is an act of obedience. If it is used for something permissible or unlawful, its ruling will be the ruling of what it was used for. A Muslim should preserve their time in the mosque and not waste it on something that is of no benefit, as it is a time when angels seek forgiveness for people and mercies descend.