Firstly: Exiting with the Whole Body without an Excuse
Whoever exits from his area of seclusion in the mosque without an excuse, need, or act of goodness to fulfil, his seclusion is nullified. Ibn Hazm has quoted consensus on this.
Secondly: Exiting with the Whole Body for a Need
Exiting for a physical or legal need, like relieving oneself and performing ablution respectively, is permissible. Consensus has been quoted over this by Ibn al-Mundhir, al-Mawardi, Ibn Qudamah, and al-Nawawi.
Thirdly: Exiting with Some of the Body
There is no harm in exiting the mosque with some of the body, and it does not affect the state of seclusion. This is by agreement of the four schools of jurisprudence.
Sexual intercourse is haram for the secluded person, and it nullifies his state therein. Consensus has been quoted on this by: Ibn al-Mundhir, al-Jassas, Ibn Hazm, Ibn `Abd al-Barr, Ibn Qudamah, al-Qurtubi, and al-Nawawi.
Fifthly: Nocturnal Emissions
Nocturnal emissions do not nullify the state of seclusion; one must simply perform ritual washing and resume his seclusion. This is by agreement of the four schools of jurisprudence.
Sixthly: Physical Contact and Kissing with Arousal
The secluded person is prohibited from kissing or physical contact with arousal. Consensus has been quoted over this matter by: Ibn al-Mundhir, al-Mawardi, Ibn `Abd al-Barr, Ibn Kathir, and al-Shawkani.
Seventhly: Sudden Menstrual or Postnatal Bleeding
Sudden menstrual or postnatal bleeding makes it haram for the woman to remain in the mosque. Her seclusion is temporarily paused due to this, but is not nullified. Once she is in a state of purity, she returns to the mosque where she was, and continues from the day she left off. This is the position of the majority: Malikis, Shafi`is, and Hanbalis.
Eighthly: Sudden Loss of Consciousness or Reason
Sudden loss of consciousness (passing out) or reason (insanity) breaks one's state of seclusion. If the afflicted returns to their original state, they resume their seclusion. This is the position of the majority: Malikis, Shafi`is, and Hanbalis.
Apostasy nullifies the state of seclusion, and this is by agreement of the four schools of jurisprudence.