Is it permissible to marry a woman after divorcing her twice and her returning by an oath of divorce, without an intermediate husband (muhallil)?

The questioner did not specify his intention for swearing by divorce, whether it was to make divorce contingent upon travel, or merely to prevent something and emphasize it, nor did he ask how to expiate his oath.

If swearing by divorce was not intended to effect divorce, but rather to prevent something and emphasize it, and scholars have issued a fatwa that divorce does not occur but an expiation is required, then it is permissible to return to the wife as long as she is within her waiting period (iddah) after the second divorce, or with a new marriage contract after her waiting period ends, provided she has not married anyone else.

It is advisable to present the matter to trustworthy scholars in person.