Those are the ones to whom We gave the Scripture and authority and prophethood. But if they [i.e., the disbelievers] deny it, then We have entrusted it to a people who are not therein disbelievers.
Ibrahim Receives the News of Ishaq and Ya`qub During His Old Age
Allah states that after Ibrahim became old and he, and his wife, Sarah, lost hope of having children, He gave them Ishaq. The angels came to Ibrahim on their way to the people of Prophet Lut (to destroy them) and they delivered the good news of a child to Ibrahim and his wife. Ibrahim's wife was amazed at the news,
(She said (in astonishment): "Woe unto me! Shall I bear a child while I am an old woman, and here is my husband, an old man Verily! This is a strange thing!" They said: "Do you wonder at the decree of Allah The mercy of Allah and His blessings be on you, O the family of Ibrahim. Surely, He (Allah) is All-Praiseworthy, All-Glorious.") 11:72-73 The angels also gave them the good news that Ishaq will be a Prophet and that he will have offspring of his own. In another Ayah, Allah said;
The subject continues through the eighth verse (89) at the end of which it has been said to comfort the Holy Prophet ﷺ ; فَإِن يَكْفُرْ بِهَا هَـٰؤُلَاءِ فَقَدْ وَكَّلْنَا بِهَا قَوْمًا لَّيْسُوا بِهَا بِكَافِرِينَ (So, if these people disbelieve it, then, We have deputed for it a people who do not disbelieve in it). In other words, it means: If some of your addressees do not listen to you and are, despite having been told about the teachings of all past prophets, bent upon nothing short of denial, then, you do not have to worry - because We have appointed a great people who would say yes to your call, follow your word and make the mission their own, and who would never stoop to the level of disbelief and denial.
Included here are all Muhajerin and Ansar present during the blessed age of the Holy Prophet ﷺ and also all Muslims who keep coming upto the end of time until comes the Qiyamah. And this verse is a fond asset for all such people, as Allah Ta` ala has named them on an occasion which calls for praise by Him:
0 Allah, make us one of them and raise us in their company.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 89–90
In Makkah, a few individuals had embraced the faith on the strength of the Prophet Muhammad’s preaching. But, as a community, the people had rejected him. Thereafter, God the Almighty softened the hearts of the people of Madinah towards his call; and they embraced the faith as a community; so much so that it became possible for him to go to Madinah and establish a centre of Islam there. This aid from Almighty God was granted to the Prophet Muhammad in its complete form. However, God can give this aid even to the successors of the Prophet who rise to follow his call. This is something which God has always done according to the requirement of His da‘is.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.