Muwatta Malik:Purity:Hadith 97
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَبْدَ اللَّهِ بْنَ مَسْعُودٍ، كَانَ يَقُولُ مِنْ قُبْلَةِ الرَّجُلِ امْرَأَتَهُ الْوُضُوءُ ‏.‏

Yahya related to me from Malik that he had heard that Abdullah ibn Masud used to say, “Wudu is necessary if a man kisses his wife.”