Authentic
hadith of Sahih Muslim
Sahih Muslim 2133e
وَحَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، بِهَذَا الإِسْنَادِ وَقَالَ " إِنَّمَا جُعِلْتُ قَاسِمًا أَقْسِمُ بَيْنَكُمْ " .
This hadith has been reported on the authority of A'mash with the same chain of transmitters but there is a slight variation (of wording) that, instead of the word Bu'ithat (I have been sent), the word ju'ilat (I have been made) has been used.
Reported by Muslim (No. 2133e, 2133c).