He is trying to understand another person, trying to enter into his position in order to find at least some common language and common
understanding. The pure heart of a person understands those around him, understands that in their lives there are difficulties that affect the character, making it not the best. Secondly, a person with a pure heart is sure to do good deeds. It is not enough just to have a good heart if it does not benefit anyone and in any way.
There is so much evil in the world, so many other people who need help, that, having a really pure heart, it is simply impossible to sit still and not help anyone. Thirdly, a person with a pure heart has a noble purpose in life. Of course, in the course of life you need to do something good, good, but all this is a trifle compared to what a person can do if he aims for something great. A person with a pure heart must have a great mind, only then can he set himself a great goal and come to its fulfillment.

And when he achieves what he planned, makes some useful invention for a person, for example, then the realization of his abilities will be considered maximum.

Of course, a person with a pure heart does not necessarily have to have everything that is written in the previous paragraph, together and at once. But, as it was said in the same place, the degree of “purity of heart” can be different. I would like to see more and more such people in the world, because the world needs purity and kindness.