And the Lord said to Aaron, "You shall have no inheritance in their land, neither shall you have any portion among them. I am your portion and your inheritance among the people of Israel." (Bemidbar / Numbers 18:20; ESV)
A key component of the life of ancient Israel was their tribal land allotments. God through Joshua apportioned the land of Israel tribe by tribe based on population distribution. God determined that the tribal clans should retain their land portions, generation by generation. Safeguards were put in place to ensure that if due to circumstances such as poverty, a clan lost a land holding, it would return to that clan eventually, after a set number of years.
This land inheritance applied to every tribe but Levi. The Levites had a special role in the life of the nation as they were set apart by God as ministers, teachers, and judges. Many would live in the proximity of the Mishkan (English: Tabernacle), the special semi-portable structure where the sacrifices were to be offered. Others of them would be scattered among the other tribes. Because of their unique place in the nation, the Levites had no land inheritance. Instead, as we read, God himself was their inheritance.
Note that their inheritance was not the special work they were called to even though this is what it was that made them unique in the nation. Their inheritance was God. But perhaps saying that God was their inheritance was just a metaphorical way to refer to the priestly service that only they were entitled to. To come to that conclusion, however, reveals a great misunderstanding of what it means to serve God.
Many years ago I met with an ultra-orthodox rabbi almost every week for a year. His commitment to his understanding of Judaism was intense. One day we were talking about the concept of having a personal relationship with God. He told me flat out that he did not, though, according to him, the leader of his particular sect did, much like the prophets of old. But as for himself, his experience of God was solely through the keeping of the mitzvot (English: commandments). Doing his God-given duty was all it meant to him to know God.
It's not that he didn't believe that God was personal. After all his venerated leader apparently had some sort of intimate relationship with God. Yet there was something about his understanding of God that prevented him from sharing his leader's experience. I don't presume to know what it is, just as I don't know what it is that is keeping anyone else from truly knowing God personally.
Some people don't think it is possible to know God personally. I wish they would read the Bible and see the intimate encounters contained within its pages and the type of people who had them - people just like you and me. Others, are like the rabbi, happily or not so happily, substituting doing things for God in place of actually knowing him. Others use highly personal, relational language. But it's not the language we use that ensures true and intimate relationship with the Master of the Universe. It's really knowing him that is what really knowing him is all about. At the same time it is the language of Scripture that properly clues us in to the reality of God he desires for us.
The Levitical inheritance of God is a case in point. That it was God himself rather than their duties that was their inheritance demonstrates for all of us that legitimate service for God stems from a personal relationship to him. Busying ourselves with good things is no substitute for truly knowing him.