Is it permissible, Islamically, for a couple to return to their marital life after being divorced three times, knowing that the first divorce was pronounced with the words "you are thrice divorced" as a threat?

If a man conditions his wife's divorce on an act or omission, and the condition occurs, then her divorce takes place. This is the view of the majority of scholars, because divorce is in the man's hands, and if he pronounces it in a clear form, it takes effect whether he is joking or serious. The proof for this is the Prophet's (peace be upon him) saying: "There are three things which, whether done seriously or in jest, are treated as serious: marriage, divorce, and رجعة (taking back one's wife)." The aforementioned woman is not permissible for her husband to marry until she marries another man willingly and that husband consummates the marriage with her and then divorces her. After her iddah (waiting period) ends, her first husband may propose to her, because she was divorced by three separate pronouncements.