Acts 7:8

‘And he gave him the covenant of circumcision. And so Abraham begat Isaac, and circumcised him the eighth day, and Isaac begat Jacob, and Jacob the twelve patriarchs.'

As a seal on these promises God gave him the covenant of circumcision (Genesis 17), which included his descendants (he ‘circumcised' Isaac). Thus came first Isaac, then Jacob and then the twelve Patriarchs, all included within the covenant and the promises. Circumcision was in order to bind them into the covenant and was thus to be seen as affecting their ‘hearts' (compare Acts 7:51).

‘Circumcised him the eighth day.' The Jews were very proud of being ‘circumcised on the eighth day'. We can compare Paul's similar claim for himself in Philippians 3:5. Abraham was thus immediately obedient to God in accordance with His commands. But as Stephen will later point out, in contrast to this God's people are later revealed as ‘uncircumcised in heart' because they were disobedient (Acts 7:51).

The first stage in God's plan is now seen as over, and God's people are living in trust and hope, without possession of the land, and will continue on in that condition for ‘four hundred years'. They are free from Babylon and truly circumcised and safe in the covenant love of God. All of this demonstrated Stephen's deep faith in the God of Israel, and in His concern for His people. This would hardly have been so of someone who was blasphemous.

(Later they will be moved beyond Babylon, will be described as uncircumcised at heart, and will be shown to have rejected the covenant, seeking to other gods. It is rather they who are blasphemous)