Hadith on Adhan: Raise your voice in call to prayer, even if alone

Abdullah ibn Abdur Rahman reported: Abu Sa’id al-Khudri, may Allah be pleased with him, said to him, “I see you love sheep and the desert. When you are among your sheep or in your desert and announce the call to prayer, raise your voice with the call. Verily, the sound of the caller’s voice is not heard by any jinn, nor human, nor anything but that it will testify for him on the Day of Resurrection. I heard it from the Messenger of Allah, peace and blessings be upon him.”

Source: Ṣaḥīḥ al-Bukhārī 584

Grade: Sahih (authentic) according to Al-Bukhari

عَنْ عَبْدِ اللَّهِ بْنِ عَبْدِ الرَّحْمَنِ أَنَّ أَبَا سَعِيدٍ الْخُدْرِيَّ قَالَ لَهُ إِنِّي أَرَاكَ تُحِبُّ الْغَنَمَ وَالْبَادِيَةَ فَإِذَا كُنْتَ فِي غَنَمِكَ أَوْ بَادِيَتِكَ فَأَذَّنْتَ بِالصَّلَاةِ فَارْفَعْ صَوْتَكَ بِالنِّدَاءِ فَإِنَّهُ لَا يَسْمَعُ مَدَى صَوْتِ الْمُؤَذِّنِ جِنٌّ وَلَا إِنْسٌ وَلَا شَيْءٌ إِلَّا شَهِدَ لَهُ يَوْمَ الْقِيَامَةِ سَمِعْتُهُ مِنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ

584 صحيح البخاري كتاب الأذان باب رفع الصوت بالنداء