After Makkah had been conquered and the Prophet had returned victorious from Tabuk, Arab delegations began to pour into the heart land of Islam. They learned about Islam, saw the character of the Messenger(sallallahu alaiyhi wassallam) of Allah, and the life-style of his Companions. Tents were erected for them in the courtyard of the mosque; they heard the Qur'an recited; watched the Muslims praying and asked the Messenger(sallallahu alaiyhi wassallam) of Allah to explain the faith to them. He impressed them with his eloquence and wisdom, and he constantly quoted verses from the Qur'an. They believed what they heard and were well satisfied. They returned to their homes full of zeal, calling on their people to accept Islam and decrying paganism and its negative effects.
Dimam ibn Tha'labah came to Madinah representing the Banu Sa'd ibn Bakr. He was a Muslim when he returned to his people and he was determined to invite them to Islam.
The first thing he said to them was, 'Al-Lat and al-Uzza are evil!'
They answered in alarm, 'Stop, Dimam! Beware of leprosy. Beware of elephantiasis! Beware of madness!'
He said, 'Confoundedly you ! By Allah, they can neither hurt nor heal. Allah has sent a Messenger(sallallahu alaiyhi wassallam) and given a Book to him through which He seeks to deliver you from your sorry state. I testify that there is no god but Allah without and associate and that Muhammad is His slave and Messenger(sallallahu alaiyhi wassallam). I have brought you what He has commanded you to do and what He has forbidden you.
Before that night was over there was not a man or a woman in his tribe who had not become a Muslim. Adi the son of Hatim, whose generosity was well-known, came to Madinah. He became a Muslim after witnessing the character and humility of the Messenger(sallallahu alaiyhi wassallam) of Allah.
'By Allah!' he said, this has nothing to do with the way all the kings behave.
The Messenger(sallallahu alaiyhi wassallam) of Allah sent Mu'adh ibn Jabal and Abu Musa to Yemen to invite the people to Islam and he advised them, 'Make things easy and not difficult. Cheer them up and do not make them afraid.'
THE OBLIGATION OF ZAKAT:
In the ninth year of the hijrah, Allah made zakat obligatory upon the Muslims.