Verso 17.517.117.217.317.417.517.617.717.817.917.1017.1117.1217.1317.1417.1517.1617.1717.1817.1917.2017.2117.2217.2317.2417.2517.2617.2717.28

Those men who practise terrific austerities not enjoined by the scriptures, given to hypocrisy and egoism, impelled by the force of lust and attachment.

Those people who practise terrible austerities not prescribed by scripture, joined to hypocrisy and ego, driven by the force of desire and passion,

Krishna now addresses a misuse of austerity (tapas). Some people undertake fierce practices not taught in scripture, motivated by hypocrisy and ego and driven by desire and attachment. The sentence continues into the next verse. The warning is relevant because extreme self-punishment can look like great holiness. Krishna suggests that harshness toward the body, when fuelled by pride, is not spiritual strength at all but another form of ego.