The Reason why these Ayat were revealed

This was revealed concerning the disbelievers among the Quraysh, when they wanted to expel the Messenger of Allah ﷺ from among themselves. So Allah issued a warning to them in this Ayah, telling them that if they expelled him, they would not stay in Makkah for very long after that. And this is what happened after he migrated from them when their persecution became so intense. Only a year and a half after that, Allah brought him and them together on the battlefield of Badr, without any pre-arranged appointment, and He caused him to prevail over them and defeat them, so he killed their leaders and took their families as captives. Hence Allah said:

سُنَّةَ مَن قَدْ أَرْسَلْنَا

The last verse (77): سُنَّةَ مَن قَدْ أَرْ‌سَلْنَا (Such has been Our way with the messengers We sent ...) tells us that, according to the customary way and law of Allah Ta` ala, when a people expel their prophet from his home-land, or compel him to leave by scaring and harassing, then, those people too are not left to continue living there. They are visited by the punishment of Allah Ta’ ala.