Sunan an-Nasa'i, Book 35b, Hadith 2 (In-Book) ⓘ
It was narrated from Al-Hasan that he disliked to hire a man without telling him what his wages would be.
أَخْبَرَنَا مُحَمَّدٌ، قَالَ أَنْبَأَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ حَمَّادِ بْنِ سَلَمَةَ، عَنْ يُونُسَ، عَنِ الْحَسَنِ، أَنَّهُ كَرِهَ أَنْ يَسْتَأْجِرَ الرَّجُلَ، حَتَّى يُعْلِمَهُ أَجْرَهُ.
also referenced under: Hadith 3858 (Reference) & Volume 4, Book 35, Hadith 3889 (DarusSalam)