sṛjaty atty avatīśvaraḥ
sa hi jātaḥ sva-setūnāṁ
gopīthāya yaduṣv ajaḥ
As stated in the Sixth Canto of the Śrīmad-Bhāgavatam (6.3.19) dharmaṁ tu sākṣād bhagavat-praṇītam: “Religion is the law established by God.” The word setu means a “boundary” or “limit,” as in the case of a dike. Earth is raised up on both sides of a river or canal so that the water will not deviate from its proper path. Similarly, God establishes laws so that people who follow them can peacefully progress along the path back home, back to Godhead. These laws, which are meant to guide human behavior, are thus called setu.
A further note on the word setu: Earth that is raised up to separate agricultural fields, or to form a causeway or bridge, is also called setu. Thus in the Ninth Canto the Bhāgavatam uses the word setu to indicate the bridge Lord Rāmacandra built to Śrī Laṅkā. Since the laws of God act as a bridge to take us from material life to liberated, spiritual life, this additional sense of the word setu certainly enriches its use here.