Good question, especially since this was one of Jesus’s repeated lines, used in a number of different circumstances. Only in one instance, a parable, does it refer to worldly goods. In most, it is clearly used to refer to knowledge. However, since it refers to both knowledge and worldly goods, it clearly is a broader rule of the way the universe works.
It occurs four times. What makes it unusual is that it is used in a variety of different contexts.
The variety of contexts are explained here (an analysis of the Greek at the links):
- Matthew 13:12 For whoever has: The context was the “secrets of the kingdom of heaven”, that were given to the apostles but told to others in parables.
- Matthew 25:29 For unto every one that hath shall be given: The context was the parable of the talents, referring to those making the most of their opportunities getting more and vice versa.
- Mark 4:25 For he that has, to him shall be given: The immediate context is getting what you given in the measure you give it.
- Luke 8:18 Take heed therefore how ye hear: The immediate context is nothing being hidden that won’t be revealed, both good and bad.
So, the larger rules echo other teachings Jesus:
- To those who asked, it is given, with the Apostles being the ones asking.
- Those who search, find. Those who take action to improve their situation are rewarded.
- Those who more you give, the more you get.
- The more you learn, the more you are in a position to learn more.