It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he (peace and blessings be upon him) said: "Whatever their families agree upon, even if it is a twig of the arak tree."
Abu Ahmad (Ibn Adi) said: Muhammad bin Abd al-Rahman bin al-Baylamani is da'if (weak) and Muhammad bin al-Harith is da'if, and the weakness of their hadith is evident. The Shaykh said: Yahya bin Ma'in and other critics of narrators said the same; and the hadith has a supporting report (shahid) through another chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14379