Allah commands His believing servants to establish prayer, which means worshipping Allah Alone with no partner or associate; to pay the Zakah, which is an act of kindness towards His poor and weak creatures; and by doing so to obey the Messenger of Allah ﷺ, i.e., to do as he commands them and to avoid what he forbids them, so that Allah will have mercy on them for that. No doubt, whoever does that, Allah will have mercy on him, as Allah says in another Ayah:
أُوْلَـئِكَ سَيَرْحَمُهُمُ اللَّهُ
(Allah will have His mercy on them) 9:71
لاَ تَحْسَبَنَّ
(Consider not) means, `do not think, O Muhammad,' that:
الَّذِينَ كَفَرُواْ
(the disbelievers) meaning, those who opposed and denied you,
مُعْجِزِينَ فِى الاٌّرْضِ
(can escape in the land.) means, that they can flee from Allah. No, Allah is able to deal with them and He will punish them most severely for that. Allah says:
وَمَأْوَاهُمُ
(Their abode) meaning, in the Hereafter,
النَّارُ وَلَبِئْسَ الْمَصِيرُ
(shall be the Fire -- and worst indeed is that destination.) means, how terrible the consequences will be for the disbelievers, how evil a place to stay in and how awful a place to rest!