Is it necessary to renew the intention of seeking reward for studying worldly sciences after a short or long interruption, or is the initial intention sufficient?

If you intend to seek reward (from Allah) at the beginning of your study and this intention remains continuous without interruption, then it persists and is not nullified by entering the restroom or eating. There is no need to renew it. However, if the intention is interrupted, it must be renewed to obtain the reward. Some scholars are of the view that the intention to seek reward at the beginning of the day suffices for all actions throughout the day that are not purely acts of worship, even if the intention is not renewed at the time of performing them.