Musnad Ahmad 32:1089

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Thabit, from Anas, who said: The Prophet, peace and blessings of Allah be upon him, took a pledge from the women when he accepted their allegiance that they would not wail. They said: "O Messenger of Allah, some women helped us (in mourning) during the Pre-Islamic period (Jahiliyyah), so may we help them in Islam?" The Prophet, peace and blessings of Allah be upon him, said: "There is no 'is'ad' (hired mourning) in Islam, no 'shighar' (a type of marriage exchange), no 'aqr' (slaughtering an animal at a grave), no 'jalab' (bringing horses for racing/gambling), and no 'janab' (avoidance/isolation). And whoever plunders, he is not of us."