It is narrated from Masruq (may Allah have mercy on him) that he went to a man who was making a bequest and was preferring some of his heirs over others. Masruq (may Allah have mercy on him) said to him: Allah Almighty has divided (the inheritance) among you well, and whoever turns away from the judgement of Allah to his own opinion has gone astray. Make a bequest for those relatives who do not inherit, then leave the wealth as Allah has divided it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12584