Hadith.2526 - Imam Jafar ibn Muhammad Al-Sadiq عليه السلام said:
"The Messenger of Allah سبحانه وتعالى (peace and blessings of Allah سبحانه وتعالى be upon him and his family) designated Al-‘Aqiq as the miqat for the people of Iraq. Its beginning is Al-Maslakhu, its middle is Ghamrah, and its end is Dhat Irq. The beginning (Al-Maslakhu) is the most virtuous."
It is not permissible to enter the state of Ihram before reaching the miqat, nor to delay it beyond the miqat except for a valid reason or out of precaution.
If a person is ill or in a state of precaution (taqiyyah), there is no harm in delaying Ihram until Dhat Irq.
