Muwatta Malik 314
Prayer in Congregation
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ دَاوُدَ بْنِ الْحُصَيْنِ، عَنِ ابْنِ يَرْبُوعٍ الْمَخْزُومِيِّ، أَنَّهُ قَالَ سَمِعْتُ زَيْدَ بْنَ ثَابِتٍ، يَقُولُ الصَّلاَةُ الْوُسْطَى صَلاَةُ الظُّهْرِ .
Yahya related to me from Malik from Da'ud ibn al-Husayn that Ibn Yarbu al-Makhzumi said, "I heard Zayd ibn Thabit say, 'The middle prayer is the prayer of dhuhr
Grading: Salim al-Hilali: Mauquf Sahih
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.