The Quran

وَما تَفَرَّقوا إِلّا مِن بَعدِ ما جاءَهُمُ العِلمُ بَغيًا بَينَهُم ۚ وَلَولا كَلِمَةٌ سَبَقَت مِن رَبِّكَ إِلىٰ أَجَلٍ مُسَمًّى لَقُضِيَ بَينَهُم ۚ وَإِنَّ الَّذينَ أورِثُوا الكِتابَ مِن بَعدِهِم لَفي شَكٍّ مِنهُ مُريبٍ

Muhammad Asad

And [as for the followers of earlier revelation,] they broke up their unity, out of mutual jealousy, only after they had come to know [the truth].¹ And had it not been for a decree that had already gone forth from thy Sustainer, [postponing all decision] until a term set [by Him], all would indeed have been decided between them [from the outset].² As it is, behold, they who have inherited their divine writ from those who preceded them³ are [now] in grave doubt, amounting to suspicion, about what it portends.⁴

Lit., "they did not break up their unity until after knowledge had come to them" - i.e., the knowledge that God is one, and that the teachings of all of His prophets were essentially the same. Cf. 2:213 and, more explicitly, 23:53, which comes immediately after the statement that "this community of yours is one single community" (see also note 30 on 23:53).
For an explanation of this passage, see note 29 on 10:19.
Lit., "who have become heirs to the divine writ after them": obviously referring to the Bible and its followers in later times.
Lit., "about it" - i.e., in doubt as to whether the relevant scripture has really been revealed by God, and, ultimately, as to whether there is any truth in the concept of "divine revelation" as such.