Question: In your first Peter lesson #2, you talk about the "12" apostles/disciples - there were actually, 13, even discounting Judas Iscariot; Paul would make twelve, and Matthias, Acts chapter 1, being the thirteenth.
Response: On the issue of the "13" disciples, it is true that Peter and company "elected" Matthias to replace Judas, but not everything recorded in the Bible that individuals do is to be taken as ordained of God (obviously - consider King Saul et al.). Peter made his share of mistakes ("don't wash my feet", "wash my whole body", etc. etc.). Every place in scripture where God makes clear His own feelings about the apostles, there are 12 (as in the 12 gates of Rev.21:14). Whose names are on the gates? If we are to imagine that one of them will have the name "Matthias", then who will be left out (certainly not Paul, the last but also the greatest of the apostles)? Remember that the election of Matthias was held before Pentecost, after which Peter (and his fellows) are suddenly much more effective for God (as one would expect with the coming of the Holy Spirit). Notice too that to "elect" Matthias, they turn to the Old Testament device of casting lots, something Jesus never did and something that is never authorized in the New Testament (or practiced elsewhere ever again). Notice that God did not communicate to Peter the need to get a new number 12 (although Peter did receive direct revelation when it was time to bring the gospel to the gentiles); and notice that when God decided to choose number 12, our Lord Jesus Christ Himself appeared to Paul in a very miraculous way that left no doubt as to God's call, God's "election" of Paul as number 12.
Through Him [Jesus Christ] we have received grace and apostleship for obedience to the faith among all nations for His name.
Romans 1:5 NKJV
Matthias was no doubt a fine believer, but he was no apostle - except in the eyes of men (and erroneously so). Perhaps it would be more helpful to say about the apostles that "God never had more than 12". Finally, in the Greek text of Acts 1:26, Luke hints that the election, while an understandable thing for these men to do in the circumstances, was not divinely sanctioned. He says of the election of Matthias that he was "voted down along with the eleven" (the verb synkatapsephizo: συγκαταψηφίζω). According to its etymology, the base verb should mean to "vote down" i.e., defeat, or, better, "to condemn". The word itself only occurs one other place in all of Greek literature (Plutarch) where it means "join in condemnation"; here we also have a passive voice so on that model it should mean "be jointly condemned with". There may be doubt on the part of some scholars about the precise meaning of the verb in this context, but according to all linguistic convention it should at the very least convey a negative connotation - something that only makes sense if we see Luke here as being careful not to endorse the election of Matthias (cf. Lk.22:3 where Judas is described as being "of the number" of the disciples [ESV, NKJV, correctly from the Greek], implying that he was not really one in fact). This is something that doesn't even show up on the radar screen in the English versions, but in the Greek it hits one squarely between the eyes. This is also evident from the very next chapter at Acts 2:14, where, in spite of Matthias' "election", Luke mentions "the eleven" instead "the twelve" – not until the calling of Paul, the genuine twelfth apostle, was the full complement again reached.
This is an important issue, because much that men have done since the days of the apostles and and tried to foist upon God in the name of "mother Church" has, in truth, been of fleshly origin and no part of the divine plan. The wrong-headed election of a twelfth apostle (something that in truth could only occur by God's will, and through Jesus' choice as in the case of all the others: Lk.6:12-16; Acts 9:15) was the first in a regrettably long series of well-meaning substitutions of human will for divine will in the administration of the Church, a trend which unfortunately continues to the present day. The crucial lesson to learn from Matthias is clear: just because human beings, even those in authority within a church, take it upon themselves to say that something is God's will does not necessarily make it so. For it is Jesus who picked the apostles, not men, and He did so "through the Holy Spirit":
(1) The first account I produced [for you], O Theophilus, dealt with all the things which Jesus did and taught from the beginning, (2) until the day when Jesus was taken up [into heaven], having given instructions to those apostles whom He had selected through the Holy Spirit.
But the Lord said to Ananias, "Go! This man (i.e., Paul) is my chosen instrument to carry my name before the Gentiles and their kings and before the people of Israel.
Acts 9:15 NIV
You might also see these links:
Are there apostles in the Church today?
The Deaths of the 12 Disciples / Apostles of Christ.
Paul is the 12th Apostle
One final point on this has to do with the procedure followed by Peter and the others. Everywhere else in the Old Testament where the lot is used, godly inquiries start by asking the general question, "should we do A or not?" (e.g. 1Sam.30:8). The question these men should have asked was "should we choose a replacement for Judas or not?", instead of, "here are two choices for you Lord, take it or leave it".
Yours in Jesus Christ,