Are there any early Judaic sources that discuss whether all firstborn sons HAVE to be redeemed, or can any firstborn son be dedicated as a priest - and NOT redeemed?
Note: Like, the Tannaim, the Mishnah, or Talmud.
At the very least, Scripture is clear that firstborn sons NOT dedicated as priests must be redeemed.
Initially, priests seem to have been taken from the "Firstborn Sons", not just Levites :
Exodus 13:2, (Shemot) - "Sanctify to Me every firstborn, every one that opens the womb among the children of Israel among man and among animals; it is Mine."
Number 3:41, (Bamidbar) - And you shall take the Levites for Me I am the Lord instead of all firstborns among the children of Israel. And [take] the Levites' animals instead of all the firstborn animals of the children of Israel.