Why Does Islam Forbid Lesbianism and Homosexuality?
Question

Could you please tell me why lesbianism and homosexuality are sins in Islam? I know they are great sins but my question is: why? I haven't been able to find the real reason? So, tell me what Allah says in the Quran and what the Prophet (peace and blessings be upon him) says in hadith about them.
Praise be to Allah.There is wisdom in what Allah has commanded and what He has forbidden 
The Muslim should not doubt, even for an instant, that what Allah has prescribed is wise. He should know that there is great wisdom in what Allah has commanded and what He has forbidden. 
It is the straight path and is the only way in which man can be safe and at peace, protecting his honour, his mind and his health, in accordance with the natural disposition (fitrah) with which Allah has created man. 
Some heretics have tried to attack Islam and its rulings; they have denounced divorce and plural marriage and permitted alcohol. Those who look at the state of their societies will see the state of misery which those societies have reached. 
When they rejected divorce, murder took its place. When they rejected plural marriage, men started to take mistresses instead. When they allowed alcohol, all kinds of shameful and immoral actions became widespread. 
Gays and lesbians go against the natural disposition
 
They (gays and lesbians) both go against the natural disposition (fitrah) which Allah has created in mankind – and also in animals – whereby the male is inclined towards the female, and vice versa.
 
Whoever goes against that goes against the natural disposition of mankind, the fitrah. 
Dangers of homosexuality and lesbianism 
The spread of homosexuality has caused man diseases which neither the east nor the west can deny exist because of them. Even if the only result of this perversion was AIDS – which attacks the immune system in humans – that would be enough. 
It also causes the breakup of the family and leads people to give up their work and study because they are preoccupied with these perversions. 
Since the prohibition has come from his Lord, the Muslim should not wait until medicine proves that harm befalls the one who does that which Allah has forbidden. Rather he must believe firmly that Allah only prescribes that which is good for people, and these modern discoveries should only increase his certainty and confidence in the greatness of Allah’s wisdom. 
Ibn al-Qayyim said: 
“Both of them – fornication and homosexuality – involve immorality that goes against the wisdom of Allah’s creation and commandment. For homosexuality involves innumerable evil and harms, and the one to whom it is done would be better off being killed than having this done to him, because after that he will become so evil and so corrupt that there can be no hope of his being reformed, and all good is lost for him, and he will no longer feel any shame before Allah or before His creation. The semen of the one who did that to him will act as a poison on his body and soul. The scholars differed as to whether the one to whom it is done will ever enter Paradise. There are two opinions which I heard Shaykh al-Islam (may Allah have mercy on him) narrate.” (al-Jawab al-Kafi, p. 115) 
What is lesbianism?
Lesbianism means one woman doing to another something like that which a man does to a woman. 
What is homosexuality?
Homosexuality means having intercourse with males in the back passage. This was the action of the accursed people of the Prophet of Allah Lut (peace be upon him). In shari’ah terminology it refers to inserting the tip of the penis into the anus of a male. 
Reference to lesbianism and homosexuality in the Quran
What is mentioned concerning these actions in the Quran and Sunnah: 
1- Allah says (interpretation of the meaning): 
“And (remember) Lut (Lot), when he said to his people: ‘Do you commit the worst sin such as none preceding you has committed in the ‘Alamin (mankind and jinn)?
Verily, you practice your lusts on men instead of women. Nay, but you are a people transgressing beyond bounds (by committing great sins)’” [al-A'raf 7:80-81]
2- “Verily, We sent against them a violent storm of stones (which destroyed them all), except the family of Lut (Lot), them We saved in the last hour of the night.” [al-Qamar 54:34 – interpretation of the meaning]
3- “And (remember) Lut (Lot), when he said to his people: ‘Do you commit the worst sin such as none preceding you has committed in the ‘Alamin (mankind and jinn)?” [al-A’raf 7:80 – interpretation of the meaning] 
And Allah says (interpretation of the meaning): 
“And (remember) Lut (Lot), when he said to his people: ‘You commit Al-Fahishah (sodomy the worst sin) which none has preceded you in (committing) it in the ‘Alamin (mankind and jinn)’” [al-‘Ankabut 29:28] 
4- “And (remember) Lut (Lot), We gave him Hukm (right judgement of the affairs and Prophethood) and (religious) knowledge, and We saved him from the town (folk) who practiced Al-Khabaith (evil, wicked and filthy deeds). Verily, they were a people given to evil, and were Fasiqun (rebellious, disobedient to Allah)” [al-Anbiya  21:74 – interpretation of the meaning] 
5- “And (remember) Lut (Lot)! When he said to his people, ‘Do you commit Al-Fahishah (evil, great sin, every kind of unlawful sexual intercourse, sodomy) while you see (one another doing evil without any screen). Do you practice your lusts on men instead of women? Nay, but you are a people who behave senselessly.’ There was no other answer given by his people except that they said: ‘Drive out the family of Lut (Lot) from your city. Truly, these are men who want to be clean and pure!’ So We saved him and his family, except his wife. We destined her to be of those who remained behind. And We rained down on them a rain (of stones). So evil was the rain of those who were warned.” [al-Naml 27:54-58 – interpretation of the meaning] 
The punishment that befell the people of Lut 
These verses refer to the punishment that befell the people of Lut . With regard to the rulings on them: 
1- Allah says (interpretation of the meaning]: 
“And the two persons (man and woman) among you who commit illegal sexual intercourse, hurt them both. And if they repent (promise Allah that they will never repeat, i.e. commit illegal sexual intercourse and other similar sins) and do righteous good deeds, leave them alone. Surely, Allah is Ever All-Forgiving (the One Who forgives and accepts repentance ), (and He is) Most Merciful.” [al-Nisa 4:16] 
Ibn Kathir said: 
“The words of Allah ‘And the two persons (man and woman) among you who commit illegal sexual intercourse, hurt them both’ mean, those who commit immoral actions, punish them both. Ibn 'Abbas (may Allah be pleased with him), Sa’id ibn Jubayr and others said: By condemning them, shaming them and hitting them with shoes. This was the ruling until Allah abrogated it and replaced it with whipping and stoning. ‘Ikrimah, ‘Ata, al-Hasan and ‘Abd-Allah ibn Kathir said: This was revealed concerning a man and woman who committed fornication. Al-Saddi said, it was revealed concerning young people before they get married. Mujahid said:  it was revealed concerning two men if they admit it bluntly; a hint is not sufficient  – as if he was referring to homosexuality. And Allah knows best.” (Tafsir Ibn Kathir, 1/463). 
Reference to lesbianism and homosexuality in the Sunnah
1- Jabir (may Allah be pleased with him) said: “The Prophet (peace and blessings of Allah be upon him) said: ‘There is nothing I fear for my ummah more than the deed of the people of Lut.’” (Narrated by al-Tirmidhi, 1457; Ibn Majah, 2563. This hadith was classed as sahih by Shaykh al-Albani (may Allah have mercy on him) in Sahih al-Jami’, no. 1552). 
2- Ibn 'Abbas said: “The Prophet (peace and blessings of Allah be upon him) said: “… cursed is the one who has intercourse with an animal, cursed is the one who does the action of the people of Lut.” (Narrated by Ahmad, 1878. This hadith was classed as sahih by Shaykh al-Albani in Sahih al-Jami’, no. 5891). 
3- Ibn 'Abbas said: “The Prophet (peace and blessings of Allah be upon him) said: ‘Whoever you find doing the deed of the people of Lut, kill the one who does it and the one to whom it is done.” (Narrated by al-Tirmidhi, 1456; Abu Dawud, 4462; Ibn Majah, 2561. This hadith was classed as sahih by Shaykh al-Albani in Sahih al-Jami’, no. 6589). 
And Allah knows best.