Narrated Ibn `Abbas (RAA): concerning the verse, “And if you are ill or on a journey...” (an-Nisa': 43). He said, "If a man sustains a wound, which he suffered during Jihad (in the cause of Allah) or ulcers, then he became junub (sexually impure) and is afraid that if he bathes he would die; he may perform ablution with clean earth (Tayammum). .
Source: sunnah.com
Other translations
Arabic
وَعَنِ ابْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا فِي قَوْلِهِ عَزَّ وَجَلَّ ﴿ وَإِنْ كُنْتُمْ مَرْضَى أَوْ عَلَى سَفَرٍ ﴾ 1 قَالَ: "إِذَا كَانَتْ بِالرَّجُلِ اَلْجِرَاحَةُ فِي سَبِيلِ اَللَّهِ وَالْقُرُوحُ, فَيُجْنِبُ, فَيَخَافُ أَنْ يَمُوتَ إِنْ اِغْتَسَلَ: تَيَمَّمَ" . رَوَاهُ اَلدَّارَقُطْنِيُّ مَوْقُوفًا, وَرَفَعَهُ اَلْبَزَّارُ, وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ, وَالْحَاكِم ُ 2 .
sunnah.com