"I heard the Messenger of Allah say: 'There is no one on earth, or under the sky, who speaks more truthfully than Abu Dharr.'" (Using translation from Ibn Mājah 156)
قَالَ رَسُولُ اللهِ ﷺ مَا أَظَلَّتِ الْخَضْرَاءُ وَلَا أَقَلَّتِ الْغَبْرَاءُ مِنْ رَجُلٍ أَصْدَقَ لَهْجَةً مِنْ أَبِي ذَرٍّ