The great purpose of the advent of the Messiah in the fulness of time was to redeem the children of men from certain consequences of the fall. For, although that experience was necessary in the development of man, and was, as has been said, a "fall upwards," it had certain consequences that called for redemption. One of these was death, from which there would have been no resurrection but for the redemption. See v. 27.
To redeem property, or a person, was, under the Mosaic law, to pay a legal ransom, and thereby to procure freedom for the land attached, or the servant in bondage. Any near relative could act as the redeemer. (See Gal. 3:13.)
Man by setting aside the commandment of God and doing the will of Satan, in the matter of the forbidden tree, became, as it were, his property, his bondservant. That appears from the word of our Lord, "No man can serve two masters ... ye cannot serve God and mammon" (Rom. 6:16.) If mankind had not had a Redeemer, it would have been in thraldom; because of the redemption, "they have become free for ever."
In the Fulness of Time. This meant, anciently, the time when the child became of age. St. Paul gives that explanation. The heir, he says, as long as he is a child, is under tutors and governors until the time appointed by the father; even so we, "but when the fulness of time was come, God sent forth his Son ... to redeem those that were under the law, that we might receive the adoption of sons, ... and the Spirit of his Son into your hearts, crying Abba, Father." (Gal. 4:4-6.) "Abba" is the Aramaic for "father," the word used by Jesus in his prayers in Gethsemane. It has been compared to our, "daddy," which, when used as a term of endearment is rather pretty and indicates intimate comradeship in the family.