"And We have certainly given you seven of the oft-repeated [verses]" - The interpretation of Qatada: It is the Opening of the Book [Al-Fatiha]; and it is seven verses. It is only called 'the oft-repeated' [al-mathani] because they are repeated in every rak'ah.
Muhammad said: It has been said: The meaning - and Allah knows best - is: 'And We have certainly given you seven [as] oft-repeated verses,' and the word 'min' [from] is redundant [silah]; just as Allah, Exalted is He, said: 'So avoid the impurity of idols' - the meaning being: avoid idols, not that only some of them are impure.
"And the Great Quran" - meaning: and We have given you the Great Quran.
﴿وَلَقَدْ آتَيْنَاكَ سَبْعًا مِنَ الْمَثَانِي﴾ تَفْسِيرُ قَتَادَةَ: هِيَ فَاتِحَةُ الْكِتَابِ؛ وَهِيَ سَبْعُ آياتٍ؛ وَإِنَّمَا سُمِّيَتِ الْمَثَانِي؛ لأَنَّهُنَّ يُثَنَّيْنَ فِي كُلِّ رَكْعَةٍ.
قَالَ محمدٌ: قِيلَ: الْمَعْنَى - وَاللَّهُ أَعْلَمُ -: وَلَقَدْ آتَيْنَاكَ سَبْعًا مَثَانِيَ، وَتَكُونُ (مَنْ) صِلَةٍ؛ كَمَا قَالَ اللَّهُ ﷿: ﴿فَاجْتَنِبُوا الرجس من الْأَوْثَان﴾ الْمَعْنَى: اجْتَنِبُوا الأَوْثَانَ، لَا أَنَّ بَعْضهَا رجسٌ.
﴿وَالْقُرْآن الْعَظِيم﴾ أَي: وآتيناك الْقُرْآن الْعَظِيم.
