Threatening to Replace the Believers With Another People if They Revert from Islam
Allah emphasizes His mighty ability and states that whoever reverts from supporting His religion and establishing His Law, then Allah will replace them with whomever is better, mightier and more righteous in Allah's religion and Law. Allah said in other Ayat,
In other words, it is said here that those who obey the commands of Allah are the People of Allah. Given to them is the good news that they will be the ones to finally overcome. The events which unfolded later on confirmed the veracity of this statement when everyone saw that the noble Companions, may Allah be pleased with them all, overcame all powers which threatened them. When internal rebellions challenged Sayyidna Abu Bakr ؓ ، Allah Almighty helped him prevail over all of them. When the towering powers of Ceaser and Cyrus marshaled their menacing might against Sayyidna ` Umar al-Faruq ؓ ، Allah Almighty effaced them from the face of the earth. Then, as long as these injunctions were dutifully observed by the Khulafa' and Muslims at large who came after them - by abstaining from establishing close bonds of friendship with non-Muslims - they had always remained winners in the struggle of life.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 56–58
If after embracing the Faith, one does not fulfill the requirements of Faith, one has, in the eyes of God, turned away from religion. The truly faithful people are those whose entire beings are so pervaded by Faith that they develop a relation with God at the level of love. Fulfillment of Islamic objectives should be so dear to them that there should be nothing but sympathy and kindness in their hearts for their brothers in Islam. They should become so kind-hearted towards Muslims that their powers and talents should never be used against them. Islamic life is a purposeful life and is therefore a life of struggle. It is the mission of a Muslim to convey the religion of God to all God’s subjects, guiding the world to keep away from the path leading to hell and to tread the path leading to paradise. In the course of carrying out this task, one has naturally to face different types of difficulties and suffer ignominy. Ultimately, two groups are formed—one consisting of those whose hearts are set in this world and the other whose focus is the Hereafter. A regular tug-of-war starts between these two groups. The test of man is that in all moments of difficulty and strife, he proves to be one who places complete reliance on God and, without caring for anybody except God, continues his spiritual journey, until that Day arrives when he shall stand accountable before God. The attention of such people centres almost entirely on God. They are steadfast in observing salat (prayer); they offer zakat (prescribed alms), and their relations with others are based on mutual well-wishing. Their bowing down before God shows that in their worldly affairs there is no egoism or arrogance. They invariably adopt an attitude of humility and on all occasions do as God desires. When people of this type come together at any one place in considerable numbers, they are destined to become dominant in that region.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.