The land which is barren i.e. on which nothing grows is called 'Upar', वृष्टि means rain. This kind of Nyaya is conceptualised keeping in view the rain on a barren land i.e. उपर
Land is of two types. On one type something can grow. There is a possibility of growing something on such land so it is known as उर्वरा भूमि fertile land. The other type of land is such on which nothing can grow. There is no possibility of growing anything on such land so it is called उपर भूमि barren land. It is very well known that rains on fertile land prove very advantageous, but rains on barren land do not prove advantageous, remain useless. On the basis of this, this 'Nyaya' explains that if anything is provided to a person who deservers it, it becomes useful. But if anything is provided to an underserving person it remains useless. So give anything to a person after finding out whether he deserves it or not.
For example there is a tree. It deserves fertilizer, land and water. So water, fertilizer and land provided to it becomes useful. But if some person offers this tree a plate of articles of food prepared from pulse, rice, chapati and vegetables the dish remains useless, as the tree does not deserve these articles of food. Thus the articles given to a person that one deserves prove useful but the articles given to a person does not deserve, remain useless.