I recently ran into a scripture that corrects some of what I have seen advocated for missionary work. I have heard various people boldly claim at times that as soon as someone says they are ready to be baptized, then they are ready, no matter how they had been living beforehand. I didn't realize there were relevant scriptures.
D&C 20:68 The duty of the members after they are received by baptism—The elders or priests are to have a sufficient time to expound all things concerning the church of Christ to their understanding, previous to their partaking of the sacrament and being confirmed by the laying on of the hands of the elders, so that all things may be done in order.
69 And the members shall manifest before the church, and also before the elders, by a godly walk and conversation, that they are worthy of it, that there may be works and faith agreeable to the holy scriptures—walking in holiness before the Lord.
Now these verses dictate a practice that we have changed, and that is fine as we believe in modern prophets. But let us look at what they say, and then apply the principles to the modern practice.
It is clear from these verses that being baptized and receiving the gift of the Holy Ghost were not done together. This dictates that before being confirmed and also before being able to partake of the sacrament (I would never have guessed those went together in the Lord's mind) the members needed to complete the following duties:
Before being confirmed, receiving the gift of the Holy Ghost, and partaking of the sacrament, members have a duty to:
1. Give sufficient time by which all things concerning the church can be expounded to their understnading
2. Prove by a godly walk and conversation that they are worthy of it. The "it" they need to prove they are worthy of is confirmation and gift of the Holy Ghost, which apparently gives them the right to partake of the sacrament. The reasoning here is that faith alone is not sufficient, they need prove that they will both have faith and also do the work of walking in holiness before the Lord.
These days we do baptism and confirmation together. How would these scriptures apply to the modern practice?
Well, they still say that before someone can be confirmed, get the gift of the Holy Ghost, and partake of the sacrament they need to have all things concerning the church expounded to them, and that they must prove by a godly walk and conversation that they are worthy of it so that the requirement of works and faith are both satisfied.
Thus this dictates that potential converts are to have time to prove that they will do the works required of the gospel covenants. For those who already are, or essentially are, doing the works required of the gospel covenants this is easy and it would take very little time. The point is that the church requires both "works and faith", not just faith, and this requirement proves they will do the works. The only way they can "dictate by a godly walk and conversation" is by having time to demonstrate that, or by having already been demonstrating it before they were converted. Otherwise, they cannot "manifest" a "godly walk and conversation" before the church.
For those who not already living close to the gospel standards, this says they should not be confirmed until they have had time to manifest not only by their faith, but by their actual works that they really will walk in holiness before the Lord. Otherwise they have not done what was necessary to prove that they were worthy to be confirmed and get the gift of the Holy Ghost. Since we now do baptism and confirmation together, and we still need people to be worthy of confirmation in the Lord's eyes before doing a confirmation, then to adapt this to the modern practice they need to be given this time before baptism as well.