The Prophet (ﷺ) said, "If somebody eats or drinks forgetfully then he should complete his fast, for what he has eaten or drunk, has been given to him by Allah."
Sahih al-Bukhari Book 30, Hadith 40
← Previous Hadith My father and I went to `Aisha and she said, "I testify that Allah's Messenger (ﷺ) at times used to get up in the morning in a state of Janaba from sexual intercourse, not from a wet dream and then he would fast that day." Then he went to Um Salama and she also narrated a similar thing.

Sahih al-Bukhari Book 30, Hadith 39 Next Hadith → I saw `Uthman performing ablution; he washed his hands thrice, rinsed his mouth and then washed his nose, by putting water in it and then blowing it out, and washed his face thrice, and then washed his right forearm up to the elbow thrice, and then the left-forearm up to the elbow thrice, then smeared his head with water, washed his right foot thrice, and then his left foot thrice and said, "I saw Allah's Apostle performing ablution similar to my present ablution, and then he said, 'Whoever performs ablution like my present ablution and then offers two rak`at in which he does not think of worldly things, all his previous sins will be forgiven."

Sahih al-Bukhari Book 30, Hadith 41