What does Genesis 17:27 mean?

This final verse of Genesis 17 repeats once more, for emphasis, that Abraham obeyed God's command completely. Every single male in his household, including those born in the household and those purchased as slaves, was circumcised right along with Abraham and Ishmael on the very day God had given that instruction. We're not told what Abraham felt about all God had revealed to him, but Abraham's full and unhesitating obedience reveals his full faith in the Lord.

One reason for this repeated emphasis might be the very nature of the command: to circumcise every male, which meant cutting off the foreskin of the penis. The natural reaction one might expect, at least from most men, is a desire to wait. "Hang on, let's think about this first.". Instead, Abraham's pointed obedience to God the very same day demonstrates how seriously he took his relationship with God.

How many men were in Abraham's household? We can't know for sure, but it likely included hundreds or more. Abraham was extremely wealthy. Years earlier, when Lot had been captured by foreign invaders, Abraham was able to raise an army of 318 trained men "born in his household" to go on the rescue mission. We must imagine that the household consisted of many more men at that time, and even more born and acquired since then.

That makes for a significant number of circumcisions in a single day with very little warning to all those men. Abraham exercised his authority and overcame whatever resistance or objections may have been raised in order to fully obey the Lord.