Sayyiduna Ibn Umar (may Allah be pleased with him) narrates from Sayyiduna Zayd bin Thabit (may Allah be pleased with him) that he (may Allah be pleased with him) said: The middle prayer means the Zuhr prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2157
Hadith Gradingمحدثین:صحيح لغيره
Hadith Takhrij«صحيح لغيره۔ اخرجه ابن جرير في تفسيره 2/569»