"As I said, the practice is inside: how you are dealing with yourself, your own affairs, your own emotions, your own happiness. That is the practice; it is not outside. Therefore, it is difficult to say.
Shantideva, who wrote the BODHICHARYAVATARA, looked as if he was a really awful student when he was at Nalanda University. He did absolutely nothing, he just slept all day. He was called Bu-Su-Ku by the other students, because he seemed to be doing nothing: these are three root syllables which, in Sanskrit, mean eating, sleeping and defecating.
The university was so embarrassed by him and found him such a disgrace that they wanted to expel him, but they couldn't find any excuse to do this because he didn't break any rules, he didn't do anything wrong. So they found an indirect way to try to cause him to leave. They made a plan to ask everybody to give a teaching and they asked him to be the first. They thought that, since he clearly didn't know anything, because he didn't study, he would feel ashamed and run away. When they asked him to give a teaching, they set up a big throne and everybody came, but just to embarrass him. But he ascended the throne and gave an amazing, beautiful teaching. They were all shocked.
So you never know whether someone else is really practising or not. Shantideva didn't do any pujas, he didn't go to any teachings, he didn't even perform any good works. That is how it was with him. But he was actually very accomplished. So therefore it is important to look at yourself."
Ringu Tulku Rinpoche in "Meeting Challenges, Unshaken by Life's Ups and Downs", Heart Wisdom Series, Bodhicharya Publications, 2018, pp107-108.