What is the ruling on frequently swearing by Allah for every little thing, such as saying, "By Allah, I am fine," or "By Allah, I will do it," and is this considered a sin?

This oath is considered to be a 'laghw al-yameen' (idle oath), for which there is no sin or expiation, based on the verse: "Allah will not impose blame upon you for what is unintentional in your oaths, but He will impose blame upon you for what you intended of oaths." (Quran 5:89) It is what slips from the tongue without intent or intention to swear. This is the opinion of the majority of scholars among the Companions, the Tabi'un (successors), and others, who derive their reasoning from the noble verse, and there is no disagreement on this matter. As for the forbidden excessive swearing, it refers to intentional and binding oaths, not 'laghw al-yameen'.