Hadithcore
Mishkat al-Masabih, 3838

‘Abdallah b. ‘Amr reported God’s Messenger as saying, “Do not sail on the sea except when going to perform the <i>hajj</i>, or the <i>‘umra</i>, or when fighting in God’s path, for under the sea there is a fire and under the fire there is a sea.” Abu Dawud transmitted it.

وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَرْكَبِ الْبَحْرَ إِلَّا حَاجًّا أَوْ مُعْتَمِرًا أَوْ غَازِيًا فِي سَبِيلِ اللَّهِ فَإِنَّ تَحْتَ الْبَحْرِ نَارًا وَتَحْتَ النَّارِ بَحْرًا» . رَوَاهُ أَبُو دَاوُدَ

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In-Book Reference
Book 19, Hadith 50