Buying a cow for the sacrificial offering

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that on the occasion of the Treaty of Hudaybiyah the people were commanded to sacrifice replacements for the sacrificial animals (that had been held back) in the year they would enter Makkah. So they replaced them, and since camels had become expensive and scarce, they were granted the concession that whoever could not find a camel could buy a cow and sacrifice it.

It is narrated from Abu Hadir al-Himyari that he said: I set out for Umrah in the year when the people of Syria were besieging Ibn al-Zubayr in Makkah, and some people of my tribe sent sacrificial animals with me. When we reached the Syrian army, they prevented us from entering the Haram, so I sacrificed the animals right there and came out of ihram. Then the following year I set out to make up my Umrah, and I asked Ibn Abbas about the matter. He said: "Offer the sacrificial animal again, for the Messenger of Allah (peace and blessings be upon him) commanded his Companions to offer, in Umrat al-Qada, replacements for the animals they had sacrificed in the year of Hudaybiyah." Amr said: My father used to be worried about this, and he would say: I do not know whether the Companions gave replacements in Umrat al-Qada for the animals of Hudaybiyah or not, until Abu Hadir narrated this hadith.
This hadith has a sahih (authentic) chain of narration, and the two Shaykhs did not record it. Abu Hadir is an acceptable (maqbul) and truthful narrator from the people of Yemen.