[Machine] It was said to the Prophet ﷺ, "Does wiping in the mosque refer to wiping over pebbles?" He replied, "If you absolutely must, then only once."  

قِيلَ لِلنَّبِيِّ ﷺ الْمَسْحُ فِي الْمَسْجِدِ يَعْنِي الْحَصَى؟ قَالَ فَقَالَ إِنْ كُنْتَ لَا بُدَّ فَاعِلًا فَوَاحِدَةً  

The Messenger of Allah said: 'Woe to the heels because of Hell-fire.'" (Using translation from Ibn Mājah 451)  

قَالَ رَسُولُ اللهِ ﷺ وَيْلٌ لِلْأَعْقَابِ مِنَ النَّارِ  

The Prophet ﷺ talked about a man leveling the earth on prostrating, and said, "If you have to do so, then do it once." (Using translation from Bukhārī 1207)  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ فِي الرَّجُلِ يُسَوِّي التُّرَابَ حَيْثُ يَسْجُدُ إِنْ كُنْتَ فَاعِلًا فَوَاحِدَةً