Sunan an-Nasa'i 3241
سنن النسائي#3241SahihIt was narrated from Abu Hurairah that the Messenger of Allah said:"None of you should propose marriage to a woman when someone else has already proposed to her, unless he marries (and he gives up the idea), or gives him permission
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 26:46