Holding Fast to Allah (I'tisam) in the Holy Quran

﴿وَٱعۡتَصِمُواْ بِحَبۡلِ ٱللَّهِ جَمِيعٗا وَلَا تَفَرَّقُواْۚ وَٱذۡكُرُواْ نِعۡمَتَ ٱللَّهِ عَلَيۡكُمۡ إِذۡ كُنتُمۡ أَعۡدَآءٗ فَأَلَّفَ بَيۡنَ قُلُوبِكُمۡ فَأَصۡبَحۡتُم بِنِعۡمَتِهِۦٓ إِخۡوَٰنٗا وَكُنتُمۡ عَلَىٰ شَفَا حُفۡرَةٖ مِّنَ ٱلنَّارِ فَأَنقَذَكُم مِّنۡهَاۗ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ لَكُمۡ ءَايَٰتِهِۦ لَعَلَّكُمۡ تَهۡتَدُونَ ﴾ [Āl-‘Imrān: 103]

(103) And hold firmly to the rope of Allah all together and do not become divided. And remember the favor of Allah upon you - when you were enemies and He brought your hearts together and you became, by His favor, brothers. And you were on the edge of a pit of the Fire, and He saved you from it. Thus does Allah make clear to you His verses that you may be guided.

Surah: Āl-‘Imrān - Verse: 103 - Juz: 4 - Page: 63

﴿وَلَا تَكُونُواْ كَٱلَّذِينَ تَفَرَّقُواْ وَٱخۡتَلَفُواْ مِنۢ بَعۡدِ مَا جَآءَهُمُ ٱلۡبَيِّنَٰتُۚ وَأُوْلَٰٓئِكَ لَهُمۡ عَذَابٌ عَظِيمٞ ﴾ [Āl-‘Imrān: 105]

(105) And do not be like the ones who became divided and differed after the clear proofs had come to them. And those will have a great punishment.

Surah: Āl-‘Imrān - Verse: 105 - Juz: 4 - Page: 63

﴿إِنَّ ٱلَّذِينَ فَرَّقُواْ دِينَهُمۡ وَكَانُواْ شِيَعٗا لَّسۡتَ مِنۡهُمۡ فِي شَيۡءٍۚ إِنَّمَآ أَمۡرُهُمۡ إِلَى ٱللَّهِ ثُمَّ يُنَبِّئُهُم بِمَا كَانُواْ يَفۡعَلُونَ ﴾ [Al-An‘ām: 159]

(159) Indeed, those who have divided their religion and become sects - you, [O Muhammad], are not [associated] with them in anything. Their affair is only [left] to Allah; then He will inform them about what they used to do.

Surah: Al-An‘ām - Verse: 159 - Juz: 8 - Page: 150

﴿وَأَطِيعُواْ ٱللَّهَ وَرَسُولَهُۥ وَلَا تَنَٰزَعُواْ فَتَفۡشَلُواْ وَتَذۡهَبَ رِيحُكُمۡۖ وَٱصۡبِرُوٓاْۚ إِنَّ ٱللَّهَ مَعَ ٱلصَّٰبِرِينَ ﴾ [Al-Anfāl: 46]

(46) And obey Allah and His Messenger, and do not dispute and [thus] lose courage and [then] your strength would depart; and be patient. Indeed, Allah is with the patient.

Surah: Al-Anfāl - Verse: 46 - Juz: 10 - Page: 183

﴿ ۞ مُنِيبِينَ إِلَيۡهِ وَٱتَّقُوهُ وَأَقِيمُواْ ٱلصَّلَوٰةَ وَلَا تَكُونُواْ مِنَ ٱلۡمُشۡرِكِينَ * مِنَ ٱلَّذِينَ فَرَّقُواْ دِينَهُمۡ وَكَانُواْ شِيَعٗاۖ كُلُّ حِزۡبِۭ بِمَا لَدَيۡهِمۡ فَرِحُونَ ﴾ [Ar-Rūm: 31-32]

(31) [Adhere to it], turning in repentance to Him, and fear Him and establish prayer and do not be of those who associate others with Allah

(32) [Or] of those who have divided their religion and become sects, every faction rejoicing in what it has.

Surah: Ar-Rūm - Verse: 31-32 - Juz: 21 - Page: 407