كتاب صلاة المسافرين وقصرها
6  
The Book of Prayer - Travellers
(13)
Chapter: It is recommended to pray Duha, the least of which is two rak`ah, the best of which is eight, and the average of which is four or six, and encouragement to do so regularly
(13)
باب اسْتِحْبَابِ صَلاَةِ الضُّحَى وَأَنَّ أَقَلَّهَا رَكْعَتَانِ وَأَكْمَلَهَا ثَمَانِ رَكَعَاتٍ وَأَوْسَطَهَا أَرْبَعُ رَكَعَاتٍ أَوْ سِتٌّ وَالْحَثِّ عَلَى الْمُحَافَظَةِ عَلَيْهَا
Sahih Muslim 719 d

A hadith like this has been narrated by Qatada with the same chain of transmitters.

وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، وَابْنُ، بَشَّارٍ جَمِيعًا عَنْ مُعَاذِ بْنِ هِشَامٍ، قَالَ حَدَّثَنِي أَبِي، عَنْ قَتَادَةَ، بِهَذَا الإِسْنَادِ مِثْلَهُ ‏.‏
Reference : Sahih Muslim 719d
In-book reference : Book 6, Hadith 96
USC-MSA web (English) reference : Book 4, Hadith 1552
  (deprecated numbering scheme)