Is it permissible for a Muslim to swear that he will not speak a truthful oath for an entire day, and continue to swear falsely on that day?

The act of a person swearing a false oath is a heinous sin. He must repent to Allah and offer expiation for the oath. If he persists in swearing false oaths, he is sinful. The majority of scholars are of the opinion that expiation is not obligatory for a false oath. He should be advised and warned about the impermissibility of his action.