What is the only qualification for being in the number of saints Paul describes?
The only qualification for being in the number of saints Paul describes is believing the Gospel: that Jesus died for our sins, was buried, and rose again. It is not church membership, baptism, or doing various works, but simply having believed the Gospel.
Les teaches from the text that Paul says, "I would not that you be ignorant," meaning not dumb or stupid but untaught; believers are to learn, understand, and know this concerning those who have died or are asleep. Paul does not add requirements such as joining the Church, being baptized, or doing this and that. The qualification for being in the number of the saints is if we have believed the Gospel—that Christ died for our sins, was buried, and rose again. Les stresses that while God expects believers to withdraw from the world and its appetites, that expectation follows salvation and is not the qualification for salvation. If believers are alive when the Lord comes, the believers who have died will also be brought with Him; they are in paradise in God's presence in soul and spirit, not bodily, waiting for the resurrection day.
For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.