Sayyiduna Ma'qil bin Yasar (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever separates is not one of us." Asad said: That is, whoever separates a mother from her child, and brothers from one another.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17669