When was the time of the Friday sermon changed from after the prayer to before it?

The Prophet (peace be upon him) used to pray Jumu'ah before thekhutbah, just like the two 'Eids, until Dihyah arrived with some merchandise. People went out to it, not thinking there was anything wrong with leaving the khutbah. So the verse was revealed: "And when they saw a transaction or a diversion, they rushed to it and left you standing." (Qur'an 62:11). After this, the Prophet presented the khutbah before the prayer and delayed the prayer.