Abu Dawud said: Hammad b. Abi Sulaiman added in his version: "When you need." But this (addition) is munkar (not authoritative).
In-book : Book 24, Hadith 114
English translation : Book 23, Hadith 3522
24. Wages (Kitab Al-Ijarah)
باب فِي الرَّجُلِ يَأْكُلُ مِنْ مَالِ وَلَدِهِ