Leaving 'Arafah before sunset: what is required of him?

Question: I stood at 'Arafah until shortly before Maghrib, and I saw the pilgrims moving toward Muzdalifah, so I went with them. One of the pilgrims warned me not to proceed at that time, but I did not listen to him. Is my Hajj valid? Or what is required of me? Please advise us, may Allah reward you with good.

Answer: If the situation is as you described in the question, and you did not return to 'Arafah after sunset, then you must sacrifice an animal in Mina or Makkah for the poor, along with repenting to Allah for that. May Allah guide them all.