When Joshua was appointed as the overseer of the nation of Israel, he was instructed to make a copy of Jehovah’s law, and he was told (as rendered in many Bible versions) to “meditate” thereon day and night. (Jos 1:8; AS, KJ, JB, RS)
... The New World Translation appropriately renders the Hebrew term ha·ghahʹ, appearing in Joshua 1:8, “you must in an undertone read.” (See also Ps 1:2.)