[23].Surah Al-Muminun [The Believers]: Ayat 52-54

৫২) আর তোমাদের এ উম্মত হচ্ছে একই উম্মত এবং আমি তোমাদের রব, কাজেই আমাকেই তোমরা ভয় করো ৷  

৫৩) কিন্তু পরে লোকেরা নিজেদের দীনকে পরস্পরের মধ্যে টুকরো করে নিয়েছে ৷ প্রত্যেক দলের কাছে যা কিছু আছে তার মধ্যেই নিমগ্ন হয়ে গেছে৷
৫৪) বেশ, তাহলে ছেড়ে দাও তাদেরকে, ডুবে থাকুক নিজেদের গাফিলতির মধ্যে একটি বিশেষ সময় পর্যন্ত৷ 

Ayat 52. And verily! Your religion (of Islamic Monotheism) is one religion, and I am your Lord, so keep your duty to Me.

Ayat 53. But they (men) have broken their religion among them into sects, each group rejoicing in its belief.

Ayat 54. So leave them in their error for a time.

[Tafseer] of ayat 52. And verily this Brotherhood of yours is a single Brotherhood. And Allah is your Lord and Cherisher: therefore fear Allah (and no other). All prophets form one Brotherhood: their Message is one, and their religion and teaching are one: they serve the One True Allah (as God), Who loves and cherishes them; and they owe their duty to Him and Him alone. in ayat 53. stern warning to people have who have cut off their affair (of unity), between them, into sects: each party rejoices in that which is with itself. The people who began to trade on the names of the prophets cut off that unity and made sects; and each sect rejoices in its own narrow doctrine, instead of taking the universal teaching of Islam the Unity from Allah. But this sectarian confusion is of man's making. It will last for a time, but the rays of Truth and Unity will finally dissipate it. in ayat 54. Allah said to leave them in their confused ignorance for a time till torment hit them. 

Hazrat Abu Zaid Thabit bin Ad-Dahhak Al-Ansari (May Allah be pleased with him) he is one of those who gave their pledge of (Rid'wan) allegiance to the Messenger of Allah [SAWW](PBUH) under the Tree) said: The Messenger of Allah [SAWW](PBUH) said, "He who swears by a religion other than that of Islam, is like what he has professed. He who kills himself with something, will be tormented with it on the Day of Resurrection. A person is not bound to fulfill a vow about something which he does not possess. Cursing a believer is like murdering him.''

[Al-Bukhari Book 08, Chapter 73, Hadith # 73]

Lesson : as mentioned above in Surah Al-Muminun Ayat 53."But they (men) have broken their religion among them into sects," "He who swears by a religion other than that of Islam'' here means either of the two things stated here. For instance, if a person says: "If I do such and such, then I am a Christian or a Jew.'' Now if he really intends to embrace Christianity or Judaism, he will immediately become so because his intention to be a Kafir (disbeliever) is Kufr (infidelity) in itself. But if the vow is meant to deny the adoption of other religions and is intended to express his firm resolution to live as a Muslim to the last even then such a vow is undesirable and is a sin for which one must seek Allah's forgiveness. The last sentence of this Hadith evidently shows that to curse a Muslim is forbidden because it is akin to killing him.