Malik ibn Anas reported: Wahb ibn Kaysan, may Allah have mercy on him, would sit with us and he would not stand to leave until he said to us, “Nothing will reform the latter of this nation except what reformed the beginning of it.”
Source: Musnad al-Muwaṭṭaʼ lil-Jawharī 1/584
عَنْ مَالِكٍ بن أنس قَالَ كَانَ وَهْبُ بْنُ كَيْسَانَ رحمه الله يَقْعُدُ إِلَيْنَا ثُمَّ لا يَقُومُ أَبَدًا حَتَّى يَقُولَ لَنَا إِنَّهُ لا يُصْلِحُ آخِرَ هَذِهِ الأُمَّةِ إِلا مَا أَصْلَحَ أَوَّلَهَا
1/584 مسند الموطأ للجوهري