The Call to Tawhid Allah says,

قُلْ

(Say) `O Muhammad, to these disbelievers and idolators,'

Toward the end of the address, both the aspects of glad tidings and of warnings of the Qur'n have been presented to them, making it clear that there are dire consequences for the mushrikin (those who associate partners with Allah) and eternal rewards for the believers. In the context of the evil fate of the Mushriks, one reason for it has been mentioned that these people did not use to pay Zakah. This gives rise to some questions. The first one is that these verses were revealed in Makkah, whereas Zakah was made obligatory in Madinah. So, how can they be accused of non-payment of Zakah before Zakah was made obligatory?

Ibn Kathir, in reply to this question, has said that Zakah, in principle, had been obligated along with Salah right from the beginning of Islam, as mentioned in Surah Muzzammil. However the determination of the Nisab (minimum capital and property for the applicability of Zakah) and the arrangements for its collection were made in Madinah. Therefore it is not correct to say that Zakah was not obligated in Makkah.