The words 'Ar-Rahman', 'Ar-Rahim' (i.e., the Most Gracious, the Most Merciful) are two words derived from 'Ar-Rahma' (i.e., the mercy). And the words 'Ar-Rahim' and 'Ar-Rāhim' have one meaning as the words 'Al-Alim' and 'Al- 'Aleem' have one and the same meaning (i.e., the Cognizant One).
الرَّحْمَنُ الرَّحِيمُ اسْمَانِ مِنَ الرَّحْمَةِ. الرَّحِيمُ وَالرَّاحِمُ بِمَعْنًى وَاحِدٍ كَالْعَلِيمِ وَالْعَالِمِ.
[Machine] The Mother of the Book was named because it begins with her writing in the scriptures and starts with her recitation in prayer. Religion is a reward for good and evil, as you do, you will be treated. Mujahid said, "Religion is judged." They are indebted.
وَسُمِّيَتْ أُمَّ الْكِتَابِ أَنَّهُ يُبْدَأُ بِكِتَابَتِهَا فِي الْمَصَاحِفِ، وَيُبْدَأُ بِقِرَاءَتِهَا فِي الصَّلاَةِ. وَالدِّينُ الْجَزَاءُ فِي الْخَيْرِ وَالشَّرِّ، كَمَا تَدِينُ تُدَانُ. وَقَالَ مُجَاهِدٌ: بِالدِّينِ بِالْحِسَابِ. {مَدِينِينَ} مُحَاسَبِينَ.
While I was praying in the Mosque, Messenger of Allah ﷺ called me but I did not respond to him. Later I said, "O Messenger of Allah ﷺ! I was praying." He said, "Didn't Allah say'--"Give your response to Allah (by obeying Him) and to His Apostle when he calls you." (8.24) He then said to me, "I will teach you a Sura which is the greatest Sura in the Qur'an, before you leave the Mosque." Then he got hold of my hand, and when he intended to leave (the Mosque), I said to him, "Didn't you say to me, 'I will teach you a Sura which is the greatest Sura in the Qur'an?' He said, "Al-Hamdu-Li l-lah Rabbi-l-ʿalamin (i.e. Praise be to Allah, the Lord of the worlds) which is Al-Sab'a Al-Mathani (i.e. seven repeatedly recited Verses) and the Grand Qur'an which has been given to me."
كُنْتُ أُصَلِّي فِي الْمَسْجِدِ فَدَعَانِي رَسُولُ اللَّهِ ﷺ فَلَمْ أُجِبْهُ فَقُلْتُ يَا رَسُولَ اللَّهِ إِنِّي كُنْتُ أُصَلِّي فَقَالَ أَلَمْ يَقُلِ اللَّهُ {اسْتَجِيبُوا لِلَّهِ وَلِلرَّسُولِ إِذَا دَعَاكُمْ} ثُمَّ قَالَ لِي لأُعَلِّمَنَّكَ سُورَةً هِيَ أَعْظَمُ السُّوَرِ فِي الْقُرْآنِ قَبْلَ أَنْ تَخْرُجَ مِنَ الْمَسْجِدِ ثُمَّ أَخَذَ بِيَدِي فَلَمَّا أَرَادَ أَنْ يَخْرُجَ قُلْتُ لَهُ أَلَمْ تَقُلْ لأُعَلِّمَنَّكَ سُورَةً هِيَ أَعْظَمُ سُورَةٍ فِي الْقُرْآنِ قَالَ {الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ} هِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ الَّذِي أُوتِيتُهُ
Messenger of Allah ﷺ said, "When the Imam says: 'Ghair-il-Maghdubi ʿalaihim Walad-Dallin (i.e. not the path of those who earn Your Anger, nor the path of those who went astray (1.7)), then you must say, 'Ameen', for if one's utterance of 'Ameen' coincides with that of the angels, then his past sins will be forgiven."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا قَالَ الإِمَامُ {غَيْرِ الْمَغْضُوبِ عَلَيْهِمْ وَلاَ الضَّالِّينَ} فَقُولُوا آمِينَ فَمَنْ وَافَقَ قَوْلُهُ قَوْلَ الْمَلاَئِكَةِ غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ