Sunan an-Nasa'i, Hadith 3859 ⓘ
It was narrated from Hammad -Ibn Abi Sulaiman- that he was asked about a man who hired a worker in return for food and he said: "No, not until he tells him (what his wages will be)."
أَخْبَرَنَا مُحَمَّدُ بْنُ حَاتِمٍ، قَالَ أَنْبَأَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ جَرِيرِ بْنِ حَازِمٍ، عَنْ حَمَّادٍ، - هُوَ ابْنُ أَبِي سُلَيْمَانَ - أَنَّهُ سُئِلَ عَنْ رَجُلٍ، اسْتَأْجَرَ أَجِيرًا عَلَى طَعَامِهِ قَالَ لاَ حَتَّى تُعْلِمَهُ.
also referenced under: Book 35b, Hadith 3 (In-Book) & Volume 4, Book 35, Hadith 3890 (DarusSalam)