It is narrated from Sayyiduna Ibn Amr (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "There is no man more truthful under the sky and upon the face of the earth than Abu Dharr (may Allah be pleased with him)."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 6630
Hadith Gradingحکم دارالسلام:حسن لغيره، وهذا إسناد ضعيف لضعف عثمان بن عمير