It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he said: "The first to rule for 'awl (proportional reduction) in the fixed shares (of inheritance) was Sayyiduna Umar (may Allah be pleased with him). By Allah! If people had given precedence to those whom Allah gave precedence and deferred those whom Allah deferred, no case of fixed shares would ever have needed 'awl." He was asked: Whom has Allah given precedence and whom has He deferred? He said: "Every heir whose share Allah, the Mighty and Majestic, never lowers from one fixed amount except to another fixed amount, these are the ones whom Allah has given precedence; and every heir whose fixed share, when it is removed (due to the presence of others), receives only what remains, these are the ones whom Allah has deferred. For example, the husband, the wife and the mother (are given precedence), and those deferred are the sisters and the daughters. So when the heirs given precedence by Allah and those deferred are gathered together, one begins with those whom He gave precedence and gives them their full right; then if anything remains, it is for those who were deferred, and if nothing remains, then there is nothing for them." This hadith is sahih (authentic) on the condition of Imam Muslim, but the two Shaykhs (Bukhari and Muslim) did not record it.