Machine summary:
[Giving fear and hope to other false sects] The preceding verses contained descriptions of the ugly conduct and rebellion of the Children of Israel and, consequently, the punishments they deserved; in this verse, the subject takes on a more general aspect and encompasses all the false sects[that] existed at that time in the Arabian Peninsula and more distant points, whether they were star worshippers, dualists, idolaters, or any other false religion, and as examples, some of them are mentioned as previously stated: It is evident that the reminders of the previous verses and the recounting of truths regarding the past currents of the Jews had created more or less fruitful effects in awakened hearts, making them unstable regarding remaining in their own religion and ready to accept Islam, just as groups such as Abdullah bin Salam and his followers abandoned the Jewish creed and turned to Islam.
Meaning: from your ancestors, that you should worship Allah alone, associate no partners or equals with Him, act according to the commands of the Torah, and believe in and acknowledge what is within it—among which is the glad tidings of the appearance of the Prophet of the End of Times and his successors; and that you should always convey this explanation and good news to your children until His appearance, so that they too, in their turn, respect these principles until the time of his mission and act upon them after his mission; just as He said in the verse: ﴿وإذ أخذ اللّه میثاق الّذین أوتوا الکتاب لتبیننّه للنّاس ولا تکتمونه﴾ (Al-Imran (3):187): And remember when Allah took a covenant from those who were given the Scripture that they would surely make it clear to the people and not conceal it.