प्रियमेकपुत्रं बध्नीयात् ॥ कZ_०१.१७.४१ ॥
priyamekaputraṃ badhnīyāt
If he has only one son, he should keep the beloved (son) under restraint/protective custody (i.e., tightly secured).
With succession concentrated in a single person, the state’s continuity becomes a single point of failure; stronger protection and control reduce coup/assassination risk.