Marking the sacrificial animal (ish'ar): is it obligatory or not?

Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that the Prophet (peace and blessings be upon him) marked (ish'ar) the hady on the right side of its hump and wiped the blood away from it.

Sayyiduna al-Miswar bin Makhramah (may Allah be pleased with him) and Marwan bin al-Hakam narrated that in the year of Hudaybiyah the Prophet (peace and blessings be upon him) garlanded the hady and marked it (ish'ar).

Ata, Tawus and Mujahid said: Marking (ish'ar) the hady is not obligatory.

Ata, Tawus and Mujahid said: If you wish, mark the animal, and if you wish, do not.

Sayyidah Aishah (may Allah be pleased with her) was asked whether the sacrificial camel should be marked (ish'ar). She said: "If he wishes, he may mark it; it is only marked so that it is known to be a sacrificial camel."

Sayyiduna Ibn Umar (may Allah be pleased with them both) said: An animal is not a hady until it has been garlanded, marked (ish'ar), and made to stand at Arafah.

Ata and Abd al-Rahman bin al-Aswad said: The hady should be covered with a blanket and then marked (ish'ar).

Sayyidah Aishah (may Allah be pleased with her) narrated that the Prophet (peace and blessings be upon him) marked (ish'ar) the hady.

Sa'id bin Jubayr said: The hady camel is both garlanded and marked (ish'ar); the hady cow is only garlanded and not marked; and the hady sheep is neither garlanded nor marked.

Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: If you wish, mark (ish'ar) the hady animal, and if you wish, do not (it is not obligatory).