Sahih Muslim 384
Sahih Muslim · Book 4: The Book of Prayers · It Is Recommended For The One Who Hears The Mu'adhdhin To Repeat His Words, Then To Send Salat Upon The Prophet (saws) And Ask Allah To Grant Him Al-Wasilah
'Abdullah b. Amr b. al-As reported Allah's Messenger (ﷺ) as saying:
حَدَّثَنَا مُحَمَّدُ بْنُ سَلَمَةَ الْمُرَادِيُّ ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ ، عَنْ حَيْوَةَ ، وَسَعِيدِ بْنِ أَبِي أَيُّوبَ ، وَغَيْرِهِمَا، عَنْ كَعْبِ بْنِ عَلْقَمَةَ ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ جُبَيْرٍ ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ الْعَاصِ ، أَنَّهُ سَمِعَ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " إِذَا سَمِعْتُمُ الْمُؤَذِّنَ فَقُولُوا مِثْلَ مَا يَقُولُ ثُمَّ صَلُّوا عَلَىَّ فَإِنَّهُ مَنْ صَلَّى عَلَىَّ صَلاَةً صَلَّى اللَّهُ عَلَيْهِ بِهَا عَشْرًا ثُمَّ سَلُوا اللَّهَ لِيَ الْوَسِيلَةَ فَإِنَّهَا مَنْزِلَةٌ فِي الْجَنَّةِ لاَ تَنْبَغِي إِلاَّ لِعَبْدٍ مِنْ عِبَادِ اللَّهِ وَأَرْجُو أَنْ أَكُونَ أَنَا هُوَ فَمَنْ سَأَلَ لِيَ الْوَسِيلَةَ حَلَّتْ لَهُ الشَّفَاعَةُ " .
When you hear the Mu'adhdhin, repeat what he says, then invoke a blessing on me, for everyone who invokes a blessing on me will receive ten blessings from Allah; then beg from Allah al-Wasila for me, which is a rank in Paradise fitting for only one of Allah's servants, and I hope that I may be that one. If anyone who asks that I be given the Wasila, he will be assured of my intercession.