Jesus says that this promise of the coming of Elijah points to John the Baptist (Matthew 11:14). Therefore, the coming of this day of the Lord must have found at least initial fulfilment in his ministry. The great and awesome day initially referred to in our text found at least initial fulfilment in the destruction of Jerusalem in AD 70. But the ultimate fulfilment will come with the return of our Lord Jesus Christ at the end of days.
5 “Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes.