What is the Sharee'ah ruling on a person who abandons Ghusl (shower taken in case of Janabah) although he is in a state of Janabah (state of major impurity due to intimate relations, a wet dream, losing consciousness, ...) and knows that he is in a state of impurity?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

In the Quran, Allaah Almighty stated that Ghusl for Janabah is obligatory. Allaah says (what means): {And if you are in a state of Janabah.} [Quran 5: 6]

When water is unavailable or one is unable to use it due to a Sharee'ah-approved justification, Tayammum (dry ablution) is the alternative. Allaah Almighty says (what means): {O you who have believed, do not approach prayer while you are intoxicated until you know what you are saying or in a state of Janabah, except those passing through [a place of prayer], until you have washed [your whole body]. And if you are ill or on a journey or one of you comes from the place of relieving himself or you have contacted women and find no water, then seek clean earth and wipe over your faces and your hands [with it]. Indeed, Allaah is ever Pardoning and Forgiving.} [Quran 4: 43]

There is also a relevant severe threat for those who abandon Ghusl for Janabah. Anas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: "Three things whoever preserves them is truly my ally and whoever neglects them is truly my enemy: prayer, fasting and [removing] Janabah." [At-Tabarani: marfoo‘ hadith]

A person who abandons Ghusl for Janabah out of denial that it is obligatory is considered an apostate. In Al-Jawab As-Saheeh, Shaykhul-Islam said:

From the indisputably known facts of Islam is that the five prayers are obligatory, making Wudhoo’ for the minor impurity and Ghusl for Janabah is obligatory, prayer is not accepted without purification while one is able to do so, Tayammum is not allowed unless one lacks water or cannot use it. Anyone who denies such obligations is judged as an apostate, according to the consensus of Muslims.

In his Tafseer (interpretation of the Quran), Ash-Shinqeeti said:

The scholars unanimously agree that a person who does not pray out of denial that prayer is obligatory is an apostate and that he has to be killed for this, unless he repents. Additionally, the preponderant opinion is that abandoning what is required for the prayer, such as Wudhoo’ and Ghusl in case of Janabah, takes the same ruling as abandoning the prayer itself. A person who denies that these prerequisites are obligatory, it is as if he denied the obligation of the prayer itself.

A person who abandons Ghusl for Janabah while he believes that it is obligatory is guilty and deserves punishment. The scholars provided different views on whether he is deemed an apostate or not. Shaykhul-Islam was asked whether Ghusl for Janabah is obligatory or not and whether it is permissible for one to pray while he is in a state of Janabah or not and he answered:

Ghusl for Janabah is obligatory and one is forbidden to pray while he is in a state of major or minor impurity unless he makes Ghusl for the first and Wudhoo’ for the second. A person who prays without that, considering his action lawful, is judged as an apostate. If he does not consider his action lawful, the scholars provided different views whether he is an apostate or not; but they unanimously agree that he deserves severe punishment. Ghusl is due when one is able to use water. If there is no water available or one fears harm for using it because of illness or severe cold, then he is required to make Tayammum and then pray. If both Ghusl and Tayammum are not available, he is allowed to pray without them and he is not required to make up for the prayer, according to the preponderant opinion. Allaah knows best.

A person who is in a state of Janabah is not allowed to perform the prayer nor make Tawaaf (circumambulating the Ka‘bah), nor touch the mus-haf (copy of the Quran), nor recite the Quran nor stay in the Masjid, until he performs Ghusl.

Allaah Knows best.