Muwatta Imam Malik (Riwayat Yahya)

Imam Malik, may Allah have mercy on him, said: Whoever forgets to fast the three days during Hajj, or is unable to fast due to illness, until he returns to his city, then if he is able to offer a sacrificial animal (hady), he should do so. Otherwise, he should fast three days at home and then fast seven more days.