सत्यं शपथो वा चलः संधिः प्रतिभूः प्रतिग्रहो वा स्थावरः इत्याचार्याः ॥ कZ_०७.१७.०३ ॥
satyaṃ śapatho vā calaḥ saṃdhiḥ pratibhūḥ pratigraho vā sthāvaraḥ ityācāryāḥ
The teachers say: a ‘movable/contingent’ treaty is (secured by) truthfulness or an oath; a ‘fixed/durable’ treaty is (secured by) a guarantor or by receiving a pledge.
Cala treaties rely on moral commitment (truth/oath) and are easier to revise or break; sthāvara treaties rely on enforceable securities (guarantor/pledge) and are harder to violate.