فَمِنْهُم مَّنْ امَنَ بِهِ
...
Of them were (some) who believed in it;
referring to Allah's favor and bounty (Prophets, Books, kingship).
...
وَمِنْهُم مَّن صَدَّ عَنْهُ
...
and of them were (some) who rejected it,
by disbelieving in it, ignoring it, and hindering the people from its path, although this bounty was from and for them, the Children of Israel. They disputed with their own Prophets; so what about you, O Muhammad, especially since you are not from the Children of Israel.
Mujahid said,
فَمِنْهُم مَّنْ امَنَ بِهِ
(Of them were (some) who believed in (him), "Muhammad,
وَمِنْهُم مَّن صَدَّ عَنْهُ
(and of them were (some) who rejected (him))."
Therefore, O Muhammad, the rejection of you because of their disbelief is even more severe and they are even further from the truth that you brought them.
This is why Allah threatened them,
...
وَكَفَى بِجَهَنَّمَ سَعِيرًا
and enough is Hell for burning (them).
meaning, the Fire is a just punishment for them because of their disbelief, rebellion and defiance of Allah's Books and Messengers.