Tikkanikayatra 9.32

9.32

pātālarkṣe rāhuketvo(tvoḥ) pure 'reto(s to)yocchittiḥ sālapātaś ca kāryaḥ/
jāmitrasthe bhūmijā(je ')syāṃśake vā putreṇendor vīkṣite 'gniḥ pradeyaḥ//

When Rāhu and Ketu occupy the asterism corresponding to the fourth house of the enemy's city, cut off the water and cause the ramparts to fall; / when Mars occupies the seventh house or its navāṃśa, aspected by the son of the Moon (Mercury), fire is to be set.