I asked Ibn ‘Abbās about Hajj Tamattu‘. He ordered me to perform it. I asked him about the Hady (sacrifice), and he said: You have to slaughter a camel, a cow, a sheep, or you may share the Hady with others. It seemed that some people disliked it

Abu Jamrah asked Ibn ‘Abbās (may Allah be pleased with both of them) about Hajj Tamattu‘, and so he ordered him to do it. Then, he asked him about the Hady associated with it, as it was mentioned in the Qur'an: {Whoever performs ‘Umrah [during the Hajj months] followed by Hajj [offers] what can be obtained with ease of sacrificial animals} [Al-Baqarah: 196]. He replied: "You have to slaughter a camel, a cow, a sheep, or one-seventh of a camel or cow." i.e. share the Hady with others.
It seems that someone had opposed Abu Jamrah regarding Tamattu‘, so he saw in his dream that someone was announcing: "May Allah accept your Hajj and accept your Hajj Tamattu‘." He went to Ibn ‘Abbās and narrated to him this beautiful vision. Since good visions are considered one part of prophet-hood, Ibn ‘Abbās (may Allah be pleased with him) was pleased with it. He considered it glad tidings that Allah guided him to what was correct. He thus said: "Allah is the Greatest. That is the Prophet's Sunnah."