Mujahid narrates from Abdullah bin Abbas (may Allah be pleased with them both) that he said: When a man enters ihram and has game with him, he should let it go.
(b) Al-Hasan said: He should release it, and if he slaughters it, he owes the compensation.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9942