Short answer
Because Allah made it sacred from the day He created the heavens and the earth, placed the Kaaba there, made it the place of Hajj and the qiblah of every prayer, and multiplied the reward of prayer in its mosque. Its sacred zone (the Haram) has its own rules: no hunting, no cutting its plants and no fighting.
Inside the Haram of Makkah, hunting land animals and cutting naturally growing green plants are haram for everyone, in ihram or not, and a penalty of their value is due. Lost property found there is announced and handled like lost property elsewhere.
Other madhhabs
- Shafi'i
- Lost property in the Haram of Makkah may be picked up only to announce it, with no time limit; the finder never takes ownership.
- Maliki, Shafi'i and Hanbali
- Madinah also has a sacred zone where hunting and cutting trees are forbidden, though most say no penalty is due. The Hanafi school holds that these Haram rules do not apply in Madinah.
Explanation
The Quran calls Makkah a safe sanctuary and the Prophet ﷺ is told to say he worships "the Lord of this city, who made it sacred". On the day of the conquest he declared that Allah made it sacred on the day He created the heavens and the earth, and that it stays sacred until the Day of Judgement.
- The first House: the Kaaba, raised by Ibrahim and Ismail, is the first house of worship for mankind.
- Hajj and qiblah: Allah made pilgrimage to it a pillar of Islam and made it the direction of every prayer.
- Reward: a prayer in the Sacred Mosque is better than a hundred thousand prayers elsewhere.
- Safety: "whoever enters it shall be safe": no fighting and no harming people there.
Rules of the Haram (Hanafi):
- Do not hunt or disturb land animals, even if you are not in ihram.
- Do not cut or uproot plants and trees that grow by themselves while they are green. Idhkhir (a fragrant grass) and what people plant are excepted.
- Sins are graver in the Haram, as good deeds are greater.
- Non-Muslims and the rules on entry are covered in can non-Muslims enter Makkah.
Madinah is the second holiest city and al-Aqsa the third. For why Muslims travel to Makkah at all, see why Muslims go to Makkah.
The evidence
Quran, Surah An-Naml 27:91
إِنَّمَآ أُمِرْتُ أَنْ أَعْبُدَ رَبَّ هَٰذِهِ ٱلْبَلْدَةِ ٱلَّذِى حَرَّمَهَا وَلَهُۥ كُلُّ شَىْءٍۢ ۖ وَأُمِرْتُ أَنْ أَكُونَ مِنَ ٱلْمُسْلِمِينَ ﴿٩١﴾
[Say, O Muhammad], "I have only been commanded to worship the Lord of this city, who made it sacred and to whom [belongs] all things. And I am commanded to be of the Muslims [those who submit to Allah]
Allah Himself made Makkah sacred.
Quran, Surah Aal-i-Imraan 3:97
فِيهِ ءَايَٰتٌۢ بَيِّنَٰتٌۭ مَّقَامُ إِبْرَٰهِيمَ ۖ وَمَن دَخَلَهُۥ كَانَ ءَامِنًۭا ۗ وَلِلَّهِ عَلَى ٱلنَّاسِ حِجُّ ٱلْبَيْتِ مَنِ ٱسْتَطَاعَ إِلَيْهِ سَبِيلًۭا ۚ وَمَن كَفَرَ فَإِنَّ ٱللَّهَ غَنِىٌّ عَنِ ٱلْعَٰلَمِينَ ﴿٩٧﴾
In it are clear signs [such as] the standing place of Abraham. And whoever enters it shall be safe. And [due] to Allah from the people is a pilgrimage to the House - for whoever is able to find thereto a way. But whoever disbelieves - then indeed, Allah is free from need of the worlds.
The Haram is a place of safety.
Quran, Surah Al-Qasas 28:57
وَقَالُوٓا۟ إِن نَّتَّبِعِ ٱلْهُدَىٰ مَعَكَ نُتَخَطَّفْ مِنْ أَرْضِنَآ ۚ أَوَلَمْ نُمَكِّن لَّهُمْ حَرَمًا ءَامِنًۭا يُجْبَىٰٓ إِلَيْهِ ثَمَرَٰتُ كُلِّ شَىْءٍۢ رِّزْقًۭا مِّن لَّدُنَّا وَلَٰكِنَّ أَكْثَرَهُمْ لَا يَعْلَمُونَ ﴿٥٧﴾
And they say, "If we were to follow the guidance with you, we would be swept from our land." Have we not established for them a safe sanctuary to which are brought the fruits of all things as provision from Us? But most of them do not know.
Makkah is a safe sanctuary provided by Allah.
Sahih al-Bukhari 1834
Sahih... لا يعضد شوكه ولا ينفر صيده ولا يلتقط لقطته إلا من عرفها ...
"Its thorn trees are not to be cut, its game is not to be disturbed, and its lost property is picked up only by one who will announce it."
The basic rules of the Haram of Makkah.
Sunan Ibn Majah 1406
Grading to be checked... وصلاة في المسجد الحرام أفضل من مائة ألف صلاة فيما سواه ...
"A prayer in the Sacred Mosque is better than a hundred thousand prayers elsewhere."
The multiplied reward of prayer in Makkah.
Where the ruling is recorded
- al-Hidaya, Kitab al-Hajj, chapter on penalties (al-jinayat), on game and plants of the Haram. Hunting and cutting green plants of the Haram require their value.
- Bada'i al-Sana'i, Kitab al-Hajj, on the game and trees of the Haram. The Hanafi view that Madinah has no Haram in the sense of these penalties.
- al-Mughni (Ibn Qudama), Kitab al-Hajj, on the Haram of Madinah. The majority view that hunting and cutting trees in Madinah's Haram are forbidden.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.