What is the ruling on one who prayed while in a state of major ritual impurity (janabah) out of embarrassment before his colleagues, and is it permissible for him to stand with them without the opening takbir (takbirat al-ihram) to avoid invalidating their prayer?

If a person in a state of major ritual impurity (junub) prays before performing ghusl, they have committed a grave sin, and their prayer is invalid due to the absence of the condition of purity (taharah). They must repent and make up the prayers they missed after incurring the state of janabah. It is not permissible for a person in a state of janabah to enter the mosque, based on the hadith: "Indeed, the mosque is not permissible for a menstruating woman nor for a person in a state of major ritual impurity." A junub person touching another person does not invalidate the prayer.