When a man is sent to another man for some reasonand he does not tell him what it is Al-Adab Al-Mufrad 1156
Arabic hadith text
حَدَّثَنَا مُحَمَّدٌ، قَالَ: أَخْبَرَنَا عَبْدُ اللهِ بْنُ زَيْدِ بْنِ أَسْلَمَ، عَنْ أَبِيهِ، عَنْ جَدِّهِ قَالَ: قَالَ لِي عُمَرُ: إِذَا أَرْسَلْتُكَ إِلَى رَجُلٍ، فَلاَ تُخْبِرْهُ بِمَا أَرْسَلْتُكَ إِلَيْهِ، فَإِنَّ الشَّيْطَانَ يُعِدُّ لَهُ كِذْبَةً عِنْدَ ذَلِكَ.
Translation
Aslam said, "'Umar said to me, 'If I send you to a man, do not tell him why I sent you to him. If you do, Shaytan will prepare a lie for him in that.'"