1) Whatever Comes Out The Private Parts Of Urine, Feces Or Wind:
Narrated Abu Hurairah (May Allah be pleased with him) Allah’s Messenger (May peace and blessings of Allah be upon him) said, “The Salat of a person who does Hadath (passes urine, stool or wind) is not accepted till he performs (repeats) the Wudu.” A person from Hadaramout asked Abu Hurairah, “What is Hadath?” Abu Hurairah replied, “Hadath means the passing of wind from the anus.”
Recorded by Bukhari, Vol. 1, Hadith-135, Page 135
This Also Includes The Release Of Al-Madhi And Al-Wadi From The Private Parts:
Abdullah ibn ‘Abbas (May Allah be pleased with him) stated: “(There is) semen, al-Wadi and al-Madhi. As for semen, it is the thing due to which one must make ghusl. As for al-Wadi and al-Madhi, he said, ‘Wash your private part or (he said private parts) and make Wudu like that for the Salah.’”
– Wadi: usually comes out due to an illness, it is a white substance that is released along with urine
– Madhi: pre-ejaculatory fluid
Recorded by Imam al-Bayhaqi. Graded Sahih by Shaykh al-Albani, Saheeh Sunan Abi Dawood, no. 190.
2) Deep Sleep (In Which A Person Is Left With No Sense Of Awareness, Regardless Of Sitting Or Lying Down):
It was narrated from ‘Ali bin Abu Taalib (May Allah be pleased with him) that the Messenger of Allah (May peace and blessings of Allah be upon him) said: “The eye is the leather strap (that ties up) the anus, so whoever falls asleep, let him perform Wudu.”
Recorded by Ibn Majah, Vol. 1, Hadith-477, Page 345. Graded as Hasan by al-Albani in Sahih Sunan Ibn Majah no. 386
3) Touching One’s Private Part, Without Any Barrier (Such As A Garment) With Desire:
Busrah bint Safwan narrated (May Allah be pleased with her) that the Prophet (May peace and blessings of Allah be upon him) said “Whoever touches his penis, then he is not to pray until he performs Wudu.”
Recorded by At-Tirmidhi who said it is Hasan Sahih, Vol. 1, Hadith-82, Page 108
Sheikh Albani (May Allah have mercy on him) mentioned: However, if it is touched with lust (desire), then the touch is not similar to touching any other part of the body, as the other parts are not usually touched with lust. And this is a matter that can clearly be noted.
Tamaam al-Minnah, p. 103
In conclusion, if the private part is touched with sexual desire, without there being any barrier, then the state of Wudu is nullified, however if the private part is touched without any sexual desire, then the person is still in a state of Wudu.
4) Eating Camel Meat:
It was narrated from Jabir bin Samurah (May Allah be pleased with him) that a man asked the Messenger of Allah (May peace and blessings of Allah be upon him): “Should I perform Wudu after eating lamb?” He said: “If you wish, then perform Wudu, and if not, then do not do it.” He said: “Should I perform Wudu after eating camel meat?” He said: “Yes, perform Wudu after eating camel meat.” He said: “Can I offer prayer in sheep pens?” He said: “Yes.” He said “Can I pray in the area where camels rest?” He said, “No.”
Recorded by Muslim, Vol. 1, Hadith-802, Page 467
5) Loss Of Consciousness Due To Insanity, Fainting, Drunkenness And Medicines:
Imam Ibn Qudaamah said: “Loss of consciousness due to insanity, fainting, drunkenness and medicines invalidates Wudu whether it is brief or long, according to scholarly consensus. Imam Ibn al-Mundhir said: ‘The scholars are unanimously agreed that the one who has fainted must do wudu’.”
Imam Ibn Qudamah in al-Mughni (1/234)
Therefore, once one loses consciousness due to sleep, he has lost his state of Wudu.