What is the legal basis for obligating the defaulting party to pay litigation fees to the aggrieved party?

The obligation of the defaulting party to pay litigation fees to the aggrieved party is based on the principle of 'no harm and no infliction of harm' (La Dharar wa la Dhirar) in Islamic Sharia, as compelling the right-holder to litigate to obtain their right is considered a harm. Islamic jurisprudential principles affirm that whoever delays the right-holder until they are compelled to file a claim, then the costs incurred by the latter as a result thereof shall be borne by the unjust defaulting party.