Does repentance suffice for one who used to swear frequently and did not offer expiation for what he swore, then repented?

Breaking an oath is not inherently forbidden. Its ruling varies depending on what was sworn upon. If one swore to perform an obligation or abstain from a forbidden act, then breaking the oath is forbidden. If one swore to perform a forbidden act or abstain from an obligation, then breaking the oath is obligatory. In the case of permissible matters, the swearer has the choice between breaking the oath and fulfilling it. Paying expiation is not a condition for the validity of repentance from breaking an oath; rather, it is a separate obligation. Repentance is remorse for the sin, coupled with the firm resolve not to return to it. If the sin relates to the rights of Allah, remorse is usually sufficient, though it may require an additional act, such as submitting oneself for punishment in the case of drinking alcohol, or submitting what was due in the case of failing to pay zakat. If it relates to the rights of people, then in addition to remorse, it is necessary to gain the person's satisfaction or to render their right to them, although some scholars hold that rendering these rights is an obligation separate from repentance and that failure to do so does not invalidate the repentance itself.