Does eating or drinking during the supererogatory (voluntary) prayer invalidate it?
Chapter on the Two Prostrations of Forgetfulness
Al-Mughni
Book of Prayer
Primary text
Intentionally eating or drinking during a supererogatory prayer invalidates it, according to the soundest opinion in the school, which is the view held by the majority of jurists. This is because whatever invalidates the obligatory prayer invalidates the voluntary one, similar to other invalidating factors.
Supporting text
A second narration from Ahmad holds that it does not invalidate the voluntary prayer. This view is narrated from Ibn al-Zubayr and Sa'id ibn Jubayr, who reportedly drank during voluntary prayer. Tawus and Ishaq share this view, reasoning that it is a minor action, resembling other non-eating actions. However, if the action is excessive, there is no dispute that it invalidates the prayer, as excessive non-eating actions invalidate prayer, making eating and drinking more likely to do so.