In one narration the words are: That increased his desire for him, and Shu'ayb (peace be upon him) said: "I intend to marry you to one of these two daughters of mine on the condition that you work for me for eight years; then if you complete ten, that is from you, and I do not intend to be hard on you. If Allah wills, you will find me among the righteous." [Surah al-Qasas: 27] meaning, good in companionship and in fulfilling what I have said. Musa (peace be upon him) said: "That is between me and you; whichever of the two terms I complete, there will be no injustice against me." [Surah al-Qasas: 28] He said: Yes. "And Allah is Guardian over what we say." [Surah al-Qasas: 28] So he (Shu'ayb, peace be upon him) married his daughter to him, and he stayed with him and worked looking after his goats.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المساقاة / 11636