The Messenger of Allah ﷺ said: When any of you goes to relieve himself, he should take with him three stones to cleans himself, for they will be enough for him. (Using translation from Abū Dāʾūd 40)
"إِذَا ذَهَبْ أحدُكُمْ إلى الغائطِ فليَذهبْ مَعَهُ بثلاثةِ أحجارٍ فليستْطِبْ بِهنَّ فإِنها تُجْزئُ عَنْه".