The Surah is so designated after the word al-bayyinah occurring at the end of the first verse.
Where it was revealed, at Makkah or Madinah, is also disputed. Some commentators say it is a Makki revelation according to most scholars; others say it is a Madani revelation according to most scholars. Ibn Az Zubair and Ata bin Yasar hold the view that it is Madani. Ibn Abbas and Qatadah are reported to have held two views, first that it is Makki, second that it is Madani. Hadrat Aishah regards it as a Makki Surah. Abu Hayyan, author of Bahr al-Muhit, and Abdul Munim ibn al- Faras, author of Ahkam al-Quran, also have preferred to regard it as Makki. As for its contents, there is nothing in it to indicate whether it was revealed at Makkah or at Madinah.
Its having been placed after Surahs Al-Alaq and Al-Qadr in the arrangement of the Quran is very meaningful. Surah Al-Alaq contains the very first revelation, while Surah Al-Qadr shows as to when it was revealed, and in this Surah it has been explained why it was necessary to send a Messenger along with this Holy Book.
First of all the need of sending a Messenger has been explained, saying: The people of the world, be they from among the followers of the earlier scriptures or from among the idolaters, could not possibly be freed from their state of unbelief, until a Messenger was sent whose appearance by itself should be a clear proof of his apostleship, and he should present the Book of God before the people in its original, pristine form, which should be free from every mixture of falsehood corrupting the earlier Divine Books; and which should comprise sound teachings.
Then, about the errors of the followers of the earlier Books it has been said that the cause of their straying into different creeds was not that Allah had not provided any guidance to them, but they strayed only after a clear statement of the Right Creed had come to them. From this it automatically follows that they themselves were responsible for their error and deviation. Now, if even after the coming of the clear statement through this Messenger, they continued to stray, their responsibility would further increase.
In this very connection, it has been stated that the Prophets who came from Allah and the, Books sent down by Him, did not enjoin anything but that the way of sincere and true service to Allah be adopted, apart from all other ways, no one else's worship, service or obedience be mixed with His, the salat be established and the zakat be paid. This same has been the true religion since ever. From this also it automatically follows that the followers of the earlier scriptures, straying from this true religion, have added extraneous things to it, which are false, and Allah's this Messenger has come to invite them back to, the same original faith.
In conclusion, it has been pointed out clearly that the followers of the earlier Books and the idolaters who would refuse to acknowledge this Messenger are the worst of creatures: their punishment is an everlasting Hell; and the people who would believe and act righteously, and would spend life in the world in awe of God, are the best of creatures: their reward is eternal Paradise wherein they will live for ever. Allah became well pleased with them and they became well pleased with Allah.
Source: Sayyid Abul Ala Maududi - Tafhim al-Qur'an - The Meaning of the Quran
إِنَّ الَّذِينَ آمَنُوا وَعَمِلُوا الصَّالِحَاتِ أُولَٰئِكَ هُمْ خَيْرُ الْبَرِيَّةِ
جَزَاؤُهُمْ عِندَ رَبِّهِمْ جَنَّاتُ عَدْنٍ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ خَالِدِينَ فِيهَا أَبَدًا ۖ رَّضِيَ اللَّهُ عَنْهُمْ وَرَضُوا عَنْهُ ۚ ذَٰلِكَ لِمَنْ خَشِيَ رَبَّهُ