This question relates to one dealt with back in June 2015, but with a slightly different slant (the original post was: "Should unbelieving spouses be baptized." A lot of good discussion. One thing that wasn't necessarily brought up in the discussion was the fact that Abraham was commanded not only to circumcise his sons but also slaves who are born in his house as well as those slaves bought with money (Genesis 17:12-13). One interesting question that I won't deal with here is: how does this fit into our understanding that we apply the covenant sign on the foundation of covenant promises? The covenant promises were made to Abraham and his children (vv7-8), but nowhere does Scripture explicitly say those promises were also extended to his slaves. Yet, the slaves were to be circumcised. Maybe someone can address that. My main question here though, is: what is the application today of the fact that Abraham was to circumcise his unbelieving ADULT slaves? If we believe in infant baptism because of Genesis 17, should we not also consider the application of the circumcision of his slaves? Obviously the world looks a bit different now. But how might this principle apply to (the ongoing discussion) of the unbelieving wives of husbands who believe in Christ? Does it not seem that the application here would entail that unbelieving wives, if yet willing and consenting, ought to indeed likewise receive the covenant sign, being part of the household; and be functionally non-communicant members of the visible church? But how does this fit together with what was pointed out about the difference between an unbelieving parent and the "holy" children of a mixed marriage in 1 Corinthians 7? Sorry, long question, but hope to get some insight.