Mishkat al-Masabih 4 Prayer كتاب الصلاة 359

وَعَن رويفع أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: مَنْ صَلَّى عَلَى مُحَمَّدٍ وَقَالَ: اللَّهُمَّ أَنْزِلْهُ الْمَقْعَدَ الْمُقَرَّبَ عِنْدَكَ يَوْمَ الْقِيَامَةِ وَجَبَتْ لَهُ شَفَاعَتِي “. رَوَاهُ أَحْمد

Ruwaih’ reported God’s Messenger as saying, “If anyone invokes a blessing on Muhammad saying, ‘O God, cause him to occupy the place near Thee on the day of resurrection’, he will be guaranteed my intercession.” Ahmad transmitted it.