1- What is the ruling on someone who jokingly swore that he was not fasting?

If the swearer is a liar, then his oath is a "Ghamus oath" (a false oath sworn knowingly to seize another's right or property), even if he was joking, and it is considered one of the major sins. The Prophet, peace and blessings be upon him, said: "The major sins are associating partners with Allah, disobedience to parents, killing a soul, and the Ghamus oath." A Muslim must abandon lying even if joking, as the Prophet, peace and blessings be upon him, said: "I guarantee a house in the middle of Paradise for one who abandons lying, even if he was joking," and his saying: "Woe to the one who speaks and lies to make people laugh thereby; woe to him, woe to him."