engaged in the enquiry into the nature of the Self
Translation
Having renounced (mentally detached from) actions the wise persons (who have learnt about Brahman at the intellectual level) – those who can restrain their minds and those engaged in the enquiry into the nature of the Self – have to make efforts for freedom from the bondage of existence
Annotation
1) The rituals told in the karma–kāṇḍa part of the Vedas are binding in nature in the sense that they lead to rebirth in order to experience the fruit of such actions. Hence they have to be renounced. 2) The word dhīra means a person who controls his mind. 3) The word ātmābhyāsa refers to the three–tier process of understanding the scripture, reflection and logical validation of it and continuously meditating on it. 4) Scriptures, no doubt, recommend rituals but they are meant only for those who have not yet attained purity of mind (Jagadguru).