The Prophet (peace and blessings be upon him) said: The most knowledgeable of my Ummah in inheritance is Zayd bin Thabit (may Allah be pleased with him)

It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The most expert in al-fara'id (the science of inheritance) in my Ummah is Zayd bin Thabit."
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that a case of a wife (widow) and parents was brought to Sayyiduna Umar (may Allah be pleased with him) (in which the deceased left a widow and his mother and father). He assigned the widow a quarter (1/4) and assigned the mother one third (1/3) of what remained.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: May Allah Almighty never see me giving preference (in inheritance) to a mother over a grandfather.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.