opanayiko [opanayiko]: Referring inwardly; to be brought inward. An epithet for the Dhamma. The Dhamma is capable of being entered upon and therefore it is worthy to be followed as a part of one’s life. - From the Dhamma Encyclopedia

I emphasise the teaching that the Dhamma is opanayiko - to be brought inside oneself - so that the mind knows, understands and experiences the results of the training within itself. If people say you are meditating correctly, don’t be too quick to believe them, and similarly, if they say you’re doing it wrong, don’t just accept what they say until you’ve really practised and found out for yourself. Even if they instruct you in the correct way that leads to enlightenment, this is still just other people’s words; you have to take their teachings and apply them until you experience results for yourself right here in the present. That means you must become your own witness, able to confirm the results from within your own mind.

It’s like the example of the sour fruit. Imagine I told you that a certain fruit tasted sour and invited you to try some of it. You would have to take a bite from it to taste the sourness. Some people would willingly take my word for it if I told them the fruit was sour, but if they simply believed that it was sour without ever tasting it, that belief would be useless (mogha), it wouldn’t have any real value or meaning. If you described the fruit as sour, it would be merely going by my perception of it. Only that. The Buddha didn’t praise such belief. But then you shouldn’t just dismiss it either: investigate it. You must try tasting the fruit for yourself, and by actually experiencing the sour taste, you become your own internal witness. Somebody says it’s sour, so you take it away and, by eating it, find out that it really is sour. It’s like you’re making double sure - relying on your own experience as well as what other people say. This way you can really have confidence in the authenticity of its sour taste; you have a witness who attests to the truth.

From Ajahn Chah’s Suffering on the Road