Valmiki Ramayana Yuddha Kanda Sarga 131 Shloka 4
Original Shlokaवारिवेगेनमहताभिन्नस्सेतुरिवक्षरन् । दुर्बन्धनमिदंमन्येराज्यच्छ्रिदमसम्वृतम् ।।6.131.4।।
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महता great, वारिवेगेन strong rush of water, भिन्नः breached, क्षरन् have no effect, सेतुरिव like dam, इदम् this, राज्यच्छ्रिदम् kingdom containing vulnerable points, असम्वृतम् not protected well, दुर्बन्धम् difficult, मन्ये I think
"If the kingdom containing vulnerable points is not protected on all sides, it can't stand, just as a strong rush of water can be prevented from breach only by constructing a dam.