أثقل شيء في الميزان الخلق الحسن
(صحيح) … [حب] عن أبي الدرداء. الصحيحة 876)
It is reported that the Messenger of Allah (peace and blessings of Allaah be upon him) said:
The most weighty thing on the Mizaan ( at Judgment Day ) will be good manners.
This hadith was narrated by Ibn Hibban (481) from the words of Abu ad-Darda, may Allah be pleased with him.
Sheikh al-Albani called the hadith authentic. See Sahih al-Jami ‘as-saghir (134), al-Silsilah al-sahihah (876).