وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ زِيَادِ بْنِ سَعْدٍ، عَنِ ابْنِ شِهَابٍ، أَنَّهُ سَمِعَهُ يَقُولُ سَدَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم نَاصِيَتَهُ مَا شَاءَ اللَّهُ ثُمَّ فَرَقَ بَعْدَ ذَلِكَ ‏.‏ قَالَ مَالِكٌ لَيْسَ عَلَى الرَّجُلِ يَنْظُرُ إِلَى شَعَرِ امْرَأَةِ ابْنِهِ أَوْ شَعَرِ أُمِّ امْرَأَتِهِ بَأْسٌ ‏.‏

Yahya related to me from Malik that Ziyad ibn Sad heard IbnShihab say, "The Messenger of Allah, may Allah bless him and grant himpeace, let his hair hang down his forehead as Allah willed, andafterwards he parted it." Malik said, "There is no harm in aman's looking at the hair of his son's wife or the hair of his wife'smother." Translation Not Available

Book reference: Muwatta Imam Malik Book 51 Hadith 1735
Web reference: Muwatta Imam Malik Book 51 Hadith 3