Sunan an-Nasa'i, Volume 4, Book 35, Hadith 3888 (DarusSalam) ⓘ
It was narrated that Abu Sa'eed said: "When you hire a worker, tell him what his wages will be."
أَخْبَرَنَا مُحَمَّدُ بْنُ حَاتِمٍ، قَالَ أَنْبَأَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ شُعْبَةَ، عَنْ حَمَّادٍ، عَنْ إِبْرَاهِيمَ، عَنْ أَبِي سَعِيدٍ، قَالَ إِذَا اسْتَأْجَرْتَ أَجِيرًا فَأَعْلِمْهُ أَجْرَهُ.
also referenced under: Hadith 3857 (Reference) & Book 35b, Hadith 1 (In-Book)