Al-Zuhri reported: When they lowered Zayd ibn Thabit, may Allah be pleased with him, into his grave, Ibn Abbas said, “Whoever would like to see how knowledge is lost, this here is the loss of knowledge.”
Source: Tārīkh Dimashq 18053
عَنِ الزُّهْرِيُّ لَمَّا دُلِّيَ زَيْدُ بْنُ ثَابِتٍ رضي الله عنه فِي قَبْرِهِ قَالَ ابْنُ عَبَّاسٍ مَنْ سَرَّهُ أَنْ يَرَى كَيْفَ يَذْهَبُ الْعِلْمُ فَهَكَذَا ذَهَابُ الْعِلْمِ
18053 تاريخ دمشق لابن عساكر