Muwatta Malik 1091
موطأ مالك#1091Sahihحَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ مُحَمَّدِ بْنِ يَحْيَى بْنِ حَبَّانَ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لاَ يَخْطُبُ أَحَدُكُمْ عَلَى خِطْبَةِ أَخِيهِ " .
Yahya related to me from Malik from Muhammad ibn Yahya ibn Habban from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "Do not ask for a woman in marriage when another muslim has already done so
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:
Salim al-HilaliSahih
In-book reference: 28:1