Hadithcore
Sunan Abi Dawud, 2423

Narrated Al-Laith:

When it was mentioned to Ibn Shihab (al-Zuhri) that fasting on Saturday had been prohibited, he would say: This is a Himsi tradition.

حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ شُعَيْبٍ، حَدَّثَنَا ابْنُ وَهْبٍ، قَالَ سَمِعْتُ اللَّيْثَ، يُحَدِّثُ عَنِ ابْنِ شِهَابٍ، أَنَّهُ كَانَ إِذَا ذُكِرَ لَهُ أَنَّهُ نُهِيَ عَنْ صِيَامِ يَوْمِ السَّبْتِ يَقُولُ ابْنُ شِهَابٍ هَذَا حَدِيثٌ حِمْصِيٌّ ‏.‏

References2 variants
In-Book Reference
Book 14, Hadith 111
English Reference
Book 13, Hadith 2417