Mishkat al-Masabih 3060
'Imran b. Husain said:
A man came to God’s Messenger and said, “My son’s son has died, so what do I receive from his estate?” He replied, “You receive a sixth;” then when he turned away he called him and said, “You receive another sixth;” and when he turned away he called him and said, “The other sixth is an allowance [beyond what is due],” (It would seem, although it is not explicit, that the grandson had left two daughters who were therefore entitled to two-thirds of the estate. The grandfather was entitled only to a sixth, but was given another sixth, as a favour, presumably because there were no other heirs).
 
Ahmad, Tirmidhi and Abu Dawud transmitted it, Tirmidhi saying this is a hasan sahih tradition.
وَعَنْ عِمْرَانَ بْنِ حُصَيْنٍ قَالَ: جَاءَ رَجُلٌ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ: إِن ابْنِي مَاتَ فَمَا لِي مِنْ مِيرَاثِهِ؟ قَالَ: «لَكَ السُّدُسُ» فَلَمَّا وَلَّى دَعَاهُ قَالَ: «لَكَ سُدُسٌ آخَرُ» فَلَمَّا وَلَّى دَعَاهُ قَالَ: «إِنَّ السُّدُسَ الْآخَرَ طُعْمَةٌ» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيُّ وَأَبُو دَاوُدَ وَقَالَ التِّرْمِذِيُّ: هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ