Musannaf Ibn Abi Shaybah

Hazrat Abu Hilal narrates that my mother made a vow that if she saw hair on my face, she would sacrifice a camel. He says, and the people of the neighborhood used to sacrifice a cow. I went to Hazrat Shurayh and asked him about this matter, so he considered both to be equal (both are the same).

It was asked from Hazrat Ata: If a person makes a vow that he is obliged to slaughter a camel for the poor, he replied that a cow will also suffice on his behalf.