Berhati mulia

By dissecting the phrase into words structure, I'll try and explain this Idioms in the most detail possible.

First is the prefix 'ber-'
Prefix 'ber-' explains that the action had already done, and it was done intentionally.

Second is the noun 'Hati'
'Hati' though literally translated to 'Liver' but in literary context, 'Hati' is used to refer to 'Heart' instead.

Lastly the word 'Mulia'
'Mulia' is a polysemous words that could mean 'Noble', 'Glorious', and 'Precious'. Though the true meaning of the words is 'Something supreme in values.'.
In this context 'Mulia' represents all three meanings.

So, we can interpret this Idiom as
'The one with the most noble, glorious, and precious heart'