مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 935
Prayer
Blessing on the Prophet, and its Excellence - Section 3
وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: مَنْ صَلَّى عَلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَاحِدَةً صَلَّى اللَّهُ عَلَيْهِ وَمَلَائِكَتُهُ سَبْعِينَ صَلَاةً. رَوَاهُ أَحْمد
‘Abdallah b. ‘Amr said, “If anyone invokes blessing on the Prophet (ﷺ) once God and His angels will grant him seventy blessings.” Ahmad transmitted it.
Mishkat al-Masabih, 935ضَعِيف (الألباني)