God hath sent forth the Spirit, &c.— St. Paul uses the same argument of proving their sonship from having the Spirit, Romans 8:16. And he that will read 2 Corinthians 4:17 and Ephesians 1:11-14 will find, that the Spirit is looked upon as the seal and assurance of the inheritance of life to those who have received the adoption of sons, as St. Paul speaks here, Galatians 4:5. The force of the argument seems to lie in this, that as he who has the spirit of a man in him, has an evidence that he is the son of man; so he that hath the Spirit of God has thereby an assurance that he is the Son of God. It was not allowed to slaves among the Jews to use the title of abba, father, in addressing the master of the family to which they belonged, or the correspondent title of imma, mother, when speaking to the mistress of it.
Related Commentaries of Galatians 4:6
Galatians 4:6
6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.