प्रस्थितागतानां च प्रवासावासकारणमनर्थ्यानां च स्त्रीपुरुषाणां चारप्रचारं च विद्युः ॥ कZ_०२.३५.१० ॥
prasthitāgatānāṃ ca pravāsāvāsakāraṇam anarthyānāṃ ca strīpuruṣāṇāṃ cārapracāraṃ ca vidyuḥ
They shall know the reasons for departure and arrival—whether for travel or residence—and shall also track the movements of spies and of suspicious/undesirable men and women.
It helps detect evasion (tax/forced service), infiltration, and criminal flight, while also regulating settlement and labour availability.