Muwatta Malik 186
موطأ مالك#186SahihThese are the words of a Companion, not of the Prophet ﷺ. The chain is graded on its own terms.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي نُعَيْمٍ، وَهْبِ بْنِ كَيْسَانَ أَنَّهُ سَمِعَ جَابِرَ بْنَ عَبْدِ اللَّهِ، يَقُولُ مَنْ صَلَّى رَكْعَةً لَمْ يَقْرَأْ فِيهَا بِأُمِّ الْقُرْآنِ فَلَمْ يُصَلِّ إِلاَّ وَرَاءَ الإِمَامِ .
Yahya related to me from Malik from Abu Nuaym Wahb ibn Kaysan that he heard Jabir ibn Abdullah say, "Someone who prays a raka without reciting the umm al-Qur'an in it has not done the prayer except behind an imam
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 3:19