Muwatta Malik, Book 15, Hadith 11 (USC-MSA)

Yahya related to me from Malik that he had heard that it took Abdullah ibn Umar eight years to learn Surat al-Baqara. (Sura 2)

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، مَكَثَ عَلَى سُورَةِ الْبَقَرَةِ ثَمَانِيَ سِنِينَ يَتَعَلَّمُهَا ‏.‏

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also referenced under: Book 15, Hadith 483 (In-Book)