وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، أَنَّهُ قَالَ رَأَيْتُ أَبِي عَبْدَ اللَّهِ بْنَ عُمَرَ يَغْتَسِلُ ثُمَّ يَتَوَضَّأُ فَقُلْتُ لَهُ يَا أَبَتِ أَمَا يَجْزِيكَ الْغُسْلُ مِنَ الْوُضُوءِ قَالَ بَلَى وَلَكِنِّي أَحْيَانًا أَمَسُّ ذَكَرِي فَأَتَوَضَّأُ ‏.‏

Yahya related from Malik from Ibn Shihab that Salim ibn Abdullahsaid, "I saw my father Abdullah ibn Umar, do ghusl and then do wudu. Isaid to him, 'Father, isn't ghusl enough for you?' He said, 'Ofcourse, but sometimes I touch my penis, so I do wudu.' " Translation Not Available

Book Ref: Muwatta Imam Malik Book 2 Hadith 94
Web Ref:  Muwatta Imam Malik Book 2 Hadith 64