It means that the person who is blameless is without blame. When the word blameless is mentioned in scripture it is always a result of someone following God. We see this in Genesis 17:1, Psalms 15:1-3, Colossians 1:22, and Philippians 2:15.
It is a promise followed up in the Qur'an, where Ishmael comes to Mecca as a founding father of Islam (see Biblical events in Mecca). The other central theme in the Abraham story is God's test of his obedience. He instructs Abraham to sacrifice to him, as a burnt offering, his beloved son Isaac.
Circumcision was enjoined upon the biblical patriarch Abraham, his descendants and their slaves as "a token of the covenant" concluded with him by God for all generations, an "everlasting covenant" (Genesis 17:13), thus it is commonly observed by two (Judaism and Islam) of the Abrahamic religions.
Abram and Sarai changed their names to signify their new office. Their names were not just a label devoid of other meaning, they were a message to anyone they were introduced to explaining who they claimed to be.
He bound his son Isaac and laid him on the altar, on top of the wood. Then he reached out his hand and took the knife to slay his son. But the angel of the LORD called out to him from heaven, "Abraham! "Do not lay a hand on the boy," he said.
Take note of this: the changing of Abraham's name is a sign from God. By changing his name, the Lord not only confirmed that he would fully carry out the promise that he made to Abraham. He, as well, made Abraham the typological father of faith for all the saints (Jude 3).
What do the details of the Lord's appearance to Abraham and Abraham's response tell about their relationship? Abraham can hear and recognize God's voice; he does not doubt that the voice is God's speaking to him. He fell facedown, this reflects his position before God Almighty; he is humble before God.