عن أبي ذر رضي الله عنه قال : قال لي النبي صلى الله عليه وآله وسلم : « قل الحق ولو كان مرا ». صححه ابن حبان من حديث طويل.
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].
Hadith Referenceبلوغ المرام / 750
Hadith Gradingمحدثین:ضعيف
Hadith Takhrij«أخرجه ابن حبان (الموارد)، حديث:94.* إبراهيم بن هشام بن يحي الغساني ضعيف متروك.»
Therefore, despite the aforementioned narration being weak in its chain, due to other supporting evidences and corroborations, it is actionable and can be used as proof.
And Allah knows best.
For further details, see: (Al-Mawsu‘ah al-Hadithiyyah, Musnad al-Imam Ahmad: 35/327, 328; and Sahih al-Targhib wa’l-Tarhib by al-Albani: 12/581, no. 2320). In this hadith, there is a command to speak the truth, no matter how many unpleasant circumstances one may face; one should not let go of truthfulness and honesty.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 750