Hadith.115 - Imam Jafar ibn Muhammad Al-Sadiq (as) said :
"When people entered the religion in large numbers, the tribe of Azd came among them with the softest hearts and the sweetest mouths.
It was asked: 'O’ Messenger of Allah (sw), we understand why they have the softest hearts, but why do they have the sweetest mouths?'
He (sw) said: 'They used to use siwak (toothstick) even in the pre-Islamic period.'"