If someone enters Makkah without ihram, what should he do?

Hazrat Ibn Abbas (may Allah be pleased with both of them) says that those who enter Makkah Mukarramah without Ihram should be sent back to the Miqat.

Hazrat Abu Al-Khalil wrote to Hazrat Saeed bin Jubair that whoever enters Makkah without Ihram will be made to wear Ihram from within Makkah itself.

Hazrat Jabir narrates that my own eyes saw that Hazrat Ibn Abbas (may Allah be pleased with them) sent him back towards the Miqat.

Hazrat Jabir bin Zaid passed by a woman who was crying. He asked, "Why are you crying?" She replied, "When I passed the Miqat, I was menstruating, so I went ahead and did not assume Ihram." He asked, "Why did you not assume Ihram?" She replied, "I was forbidden to do so." He said, "Then go and assume Ihram from another place (Miqat)."

Ibrahim says regarding the person who enters Makkah neither for Hajj nor for Umrah, and he fears that if he goes back to the Miqat, he will miss it, then he should assume Ihram from that very place, and he did not mention any penalty (dam) for him.

Hazrat Wabra narrates that a man entered Makkah Mukarramah wearing clothes, and when the time for Hajj arrived, he feared that if he went to the Miqat, he would miss Hajj. So Ibn Zubair instructed him to assume Ihram from his current place. Then, after performing Hajj, he should go to the Miqat and assume Ihram for Umrah.

Hasan was asked about a person who, out of ignorance, entered Makkah without Ihram. Most often, his opinion was that he should assume Ihram from that very place. Sometimes he would say that he should return to the Miqat and assume Ihram from there. However, if he fears missing Hajj, then he should assume Ihram from where he is, and there is nothing upon him.

Hazrat Ata says that he should enter into Ihram from there, and a sacrificial animal (dam) becomes obligatory upon him.