The preference for garlanding and marking sacrificial animals

Sayyiduna Miswar bin Makhramah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) set out in the year of al-Hudaybiyah with more than a thousand of his Companions. When he came to Dhu al-Hulayfah, he garlanded the sacrificial animals, marked them (ish'ar) and entered ihram.
Qiladah: a mark on a sacrificial animal that is designated for the House of Allah.
Ish'ar: drawing blood from the right side of a camel's hump and smearing it over it.

Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) prayed the Zuhr prayer at Dhu al-Hulayfah; then his sacrificial camel was brought, and he marked (ish'ar) the right side of its hump, then wiped the blood from it, then garlanded it with two sandals. Then his mount was brought, and when it rose upon al-Bayda', he made the talbiyah for Hajj. [Sahih: Muslim: 1243]

Yahya narrated this hadith from Shu'bah, (saying) that he (peace and blessings be upon him) wiped away the blood with his hand.
(b) Abu Dawud said that Hammam narrated from Qatadah that he (peace and blessings be upon him) wiped away the blood with his finger.

Nafi' (may Allah have mercy on him) narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that when he brought a sacrificial animal from Madinah, he would garland it and mark it (ish'ar) at Dhu al-Hulayfah; he would garland it before marking it, do both in one place, and do them while facing the qiblah. He would garland it with two sandals and mark it on the left side of the hump. Then the sacrificial animals would be driven along with him, then he would stand at Arafah with the people, and then depart from there with the people. When he departed, and when he came to Mina on the morning of the day of sacrifice, he would sacrifice before shaving the head or cutting the hair, and he would sacrifice with his own hand. He would line them up standing and face them towards the qiblah, then he would eat and feed others.

Nafi' narrated from Abdullah bin Umar (may Allah be pleased with them both) that he would mark (ish'ar) the sacrificial camels on the left side of the hump, unless they were unruly and shied away; then, if he was not able to get between them, he would mark them on the right side. When he intended to mark them, he would face the qiblah. When marking them, he would say: 'Bismillah wallahu akbar' (In the name of Allah, and Allah is the Greatest). He would mark them with his own hand and slaughter them (the camels) standing, with his own hand.

Nafi' narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he did not mind whether the ish'ar was done on the right side or the left.
Imam al-Shafi'i (may Allah have mercy on him) said, in other than this narration: The ish'ar should be done on the right side of the hump, because that is how the Messenger of Allah (peace and blessings be upon him) performed the ish'ar.

Nafi' narrated that Abdullah bin Umar (may Allah be pleased with them both) said: The sacrificial animal (hady) is that which is garlanded, marked (ish'ar), and taken to stand at Arafah. [Sahih. Recorded by Malik: 849]

Al-Qasim bin Muhammad and Amrah bint Abd al-Rahman narrated from Sayyidah Aishah (may Allah be pleased with her) that the sacrificial animal is only that which is garlanded, marked (ish'ar), and taken to stand at Arafah.

Sayyiduna Ali (may Allah be pleased with him) is also reported to have said the same.

Aswad (may Allah have mercy on him) narrated from Aishah (may Allah be pleased with her) that the sacrificial camel is marked (ish'ar) only so that it may be known that it is a sacrifice for the House of Allah.

Ibrahim (may Allah have mercy on him) said that Aswad (may Allah have mercy on him) sent his slave to Sayyidah Aishah (may Allah be pleased with her) to ask about sacrificial camels: should they be taken to stand at Arafah? She said: If you wish, do so; and if you do not wish, then do not.