At the exact perfect timing, God sent His Son to fulfill His redemptive plan for humanity! We are told it was so we might receive adoption as sons. When Paul wrote this, he likely had in mind the Roman custom that adopted children were given equal privileges and promised an inheritance. Adoption was final and irrevocable. It was public and, believe it or not, adopted sons held a stronger position in the family than birth sons!
You are no longer a slave, but God has made you an heir (Galatians 4:7). Everything God owns belongs to you because you belong to Him. Your eternal inheritance as co-heir with Christ is the result of the amazing grace of your incredible Father.
“But when the fullness of time had come, God sent forth His Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons.” Galatians 4:4-5