Muwatta Malik
Purity
Hadith #37
2.37
وَحَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ جَابِرَ بْنَ عَبْدِ اللَّهِ الأَنْصَارِيَّ، سُئِلَ عَنِ الْمَسْحِ، عَلَى الْعِمَامَةِ فَقَالَ لاَ حَتَّى يُمْسَحَ الشَّعْرُ بِالْمَاءِ .
Yahya related to me from Malik that he had heard that Jabir ibn Abdullah al-Ansari was asked about wiping over a turban. He said, "Not unless you have wiped over your hair with water