Bhagavad Gita · Karma YogaChapter 3, Shloka 12 (3.12)

Who is the thief? One who enjoys apradāya — without giving back, without offering.

Shankaracharya: ānṛṇyam akṛtvā — without repaying the debt; sva-deha-indriyāṇy eva tarpayati — he gratifies only his own body and senses — taskara eva saḥ deva-ādi-sva-apahārī — he is a thief, one who steals what belongs to the gods and others. (Here, as examples of "desired enjoyments", Shankara lists strī-paśu-putrādīn — this is the language of his time, in which women were placed on a list of enjoyments; this book does not accept that view, and it is mentioned only to give a faithful account of the commentary.)

Acharya Ramanuja — a definition of theft. Ramanuja gives a very precise definition of theft: cauryaṃ hi nāma anyadīye tat-prayojanāya eva pariklṛpte vastuni svakīyatā-buddhiṃ kṛtvā tena svātma-poṣaṇam — theft means this: taking a thing that belongs to someone else, and is kept for that person's purpose, regarding it as "mine", and nourishing oneself with it. And he says that such a person not only becomes unfit for the highest human goal but also niraya-gāmitvaṃ ca — heads towards hell.