Is everything that is harmful for oneself haram?
Please add references that prove that whatever is harmful for oneself is haram.
Definition of harmful:
Like smoking, eating certain food, or "too much" of certain food.
Yes, the basic Islamic principle is that everything that is proven to be harmful is haram.
The evidence for the prohibition of that which is harmful is to be found in the Qur’an and the Sunnah.
Allah says in Surah Al-Baqarah:
“and do not throw yourselves into destruction”
In Surah An-Nisa:
“And do not kill yourselves (nor kill one another)”
The prohibition on killing oneself is also a prohibition on the means of doing so. Whatever causes harm is haram.
The Prophet (blessings and peace of Allah be upon him) said:
“There should be neither harming nor reciprocating harm.”