"I heard the Messenger of Allah [SAW] say: 'Allahumma, inni a'udhu bi-'azamatika an ughtala min tahti (O Allah, I seek refuge in Your greatness from being swallowed up from beneath me.)'"  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ اللَّهُمَّ إِنِّي أَعُوذُ بِعَظَمَتِكَ أَنْ أُغْتَالَ مِنْ تَحْتِي قَالَ جُبَيْرٌ وَهُوَ الْخَسْفُ قَالَ عُبَادَةُ فَلاَ أَدْرِي قَوْلَ النَّبِيِّ ﷺ أَوْ قَوْلَ جُبَيْرٍ  

"The Prophet [SAW] used to say: 'Allahumma (O Allah,)' and he mentioned the supplication, and said at the end, 'A'udhu bika an ughtala min tahti (and I seek refuge with You from being swallowed up from beneath me.)'"  

كَانَ النَّبِيُّ ﷺ يَقُولُ اللَّهُمَّ فَذَكَرَ الدُّعَاءَ وَقَالَ فِي آخِرِهِ أَعُوذُ بِكَ أَنْ أُغْتَالَ مِنْ تَحْتِي يَعْنِي بِذَلِكَ الْخَسْفَ