If someone does something against his oath due to forgetfulness

Narrated Ibn `Abbas: A man said to the Prophet (while he was delivering a sermon on the Day of Nahr), "I have performed the Tawaf round the Ka`ba before the Rami (throwing pebbles) at the Jamra." The Prophet (ﷺ) said, "There is no harm (therein)." Another man said, "I had my head shaved before slaughtering (the sacrifice)." The Prophet (ﷺ) said, "There is no harm." A third said, "I have slaughtered (the sacrifice) before the Rami (throwing pebbles) at the Jamra." The Prophet (ﷺ) said, "There is no harm."