وليعلم الذين أوتوا العلم أنه الحق من ربك فيومنوا به
And that those who have been given knowledge may know that it is the truth from your Lord, so that they may believe therein,
means, `so that those who have been given beneficial knowledge with which they may differentiate between truth and falsehood, those who believe in Allah and His Messenger, may know that what We have revealed to you is the truth from your Lord, Who has revealed it by His knowledge and under His protection, and He will guard it from being mixed with anything else.' Indeed, it is the Wise Book which,
ﻻ يٲتيه البطل من بين يديه وﻻ من خلفه تنزيل من حكيم حميد
Falsehood cannot come to it from before it or behind it, (it is) sent down by the All-Wise, Worthy of all praise (Allah). (41:42)
فيومنوا به
(so that they may believe therein),
means, that they may believe that it is true and act upon it.
فتخبت له قلوبهم
and their hearts may submit to it with humility.
means, that their hearts may humble themselves and accept it.
وإن الله لهاد الذين آمنوا إلى صراط مستقيم
And verily, Allah is the Guide of those who believe, to the straight path.
means, in this world and in the Hereafter. In this world, He guides them to the truth and helps them to follow it and to resist and avoid falsehood; in the Hereafter, He will guide them to the straight path which leads to the degrees of Paradise, and He will save them from the painful torment and the dismal levels of Hell