بُلُوغُ الْمَرَامِ
Bulugh al-Maram 888
Business Transactions
عَنْ أَبِي ذَرٍّ - رضى الله عنه - قَالَ: قَالَ لِي رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ قُلِ اَلْحَقَّ, وَلَوْ كَانَ مُرًّا } صَحَّحَهُ اِبْنُ حِبَّانَ فِي حَدِيثٍ طَوِيلٍ [1] .
Narrated Abu Dhar (RA): Allah's Messenger (ﷺ) said to me, "Say the truth even though it is bitter (i.e. difficult to admit)." [Ibn Hibban graded it Sahih (authentic) as a part of a long Hadith].
Sunnah.com reference: Book 7, Hadith 132