Here's more of the passage because I think posting a single verse is seldom very helpful.

(Galatians 4:1-7 NIV) What I am saying is that as long as the heir is a child, he is no different from a slave, although he owns the whole estate. {2} He is subject to guardians and trustees until the time set by his father. {3} So also, when we were children, we were in slavery under the basic principles of the world. {4} But when the time had fully come, God sent his Son, born of a woman, born under law, {5} to redeem those under law, that we might receive the full rights of sons. {6} Because you are sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, "Abba, Father." {7} So you are no longer a slave, but a son; and since you are a son, God has made you also an heir.