Assalamu’alaykumWhat is the ruling on consuming nabidh from soaked grapes/dates/any other fruit that has been fermented for over 3 days? We usually soaked some fruit with water and let them to be fermented for several days until a foam/froth formed on top of the fluid, then using it as a natural yeast for bread leavening agent (as a substitution for a dry yeast).Jazaakumullah khairan for the answer. May Allah bless you

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.

According to Ibn Al-Atheer in An-Nihaayah, Nabeeth is defined as follows: “Drinks made from dates, raisins, honey, wheat, barley, and others. When dates or grapes are soaked in water, the (resulting) drink is called Nabeeth regardless of whether it is intoxicating or not.” [End of quote]

The Nabeeth mentioned in the question has apparently turned into Khamr (intoxicant) and was left for more than three days, and according to the Sharee‘ah, this is unlawful for consumption. Ibn Qudaamah said in Al-Mughni (Ed. Cairo Bookshop) (9/170): “Nabeeth is lawful for consumption as long as it has not been boiled nor left (soaked) for three days. Nabeeth is the water in which dates or raisins or their like are soaked to make the water sweet and to take its salinity away. There is nothing wrong with drinking it as long as it has not been boiled or soaked for three days … because after three days, it becomes intoxicating, and every intoxicant is unlawful for consumption.” [End of quote]

The foam that you mentioned is that of Khamr, and it is ritually impure and must not be used in anything. If it is added to anything that is ritually pure, it contaminates it and renders it ritually impure.

Allah Knows best.