Is it permissible for someone who entered Mecca twenty days before the Day of Arafah to enter into a state of Ihram from Mecca, or is it obligatory for him to enter into Ihram from his designated Miqat?

Whoever intends to enter Mecca for Hajj or Umrah must enter into ihram from the miqat of their country, even if they intend to enter long before Hajj. It is not permissible to pass the miqat without ihram. The miqats are those designated by the Messenger of Allah, peace and blessings be upon him. It is permissible to enter into ihram for Umrah from the miqat, then exit from ihram, and remain in Mecca until the time for entering into ihram for Hajj arrives. One then enters into ihram from Mecca, thereby becoming a Mutamatti'.