Mark 9:49–50 consists of three of Jesus’ most enigmatic statements.
1. Everyone will be salted with fire.
2. Salt is good, but if it loses its saltiness, how can you make it salty again?
3. Have salt in yourselves, and be at peace with each other.
##1 & 3 occur nowhere else in the Bible, not even in Synoptic parallels.
#2 occurs in Matthew and Luke—but in different contexts:
Matt 5:13, in the Sermon on the Mount
Luke 13:34, parable of counting the cost
This might suggest that we are dealing with a topical collection of related sayings in Mark 9. The first saying is the only verse in the Bible that connects salt and fire. The use of fire is not unexpected since that word has been in the context multiple times (vv. 43, 48). It is the addition of “fire” that marks a disjunction with the immediately preceding verses. Had v. 49 said, “everyone will be burned with fire,” then we would likely explain the statement as related to everyone who is thrown into hell (v. 47), but the change of metaphors to being “salted with fire” suggests a new thought here.
Since v. 49 does begin with γάρ (for), there should be a connection with the preceding context, but it may not be the immediately preceding verses, but to the larger context, perhaps vv. 33–48 in which Jesus is teaching regarding discipleship. Since this context is dealing with discipleship, we should probably assume that these sayings also relate to that theme.
The only other passage where the two ideas of fire and salt are connected is in connection with the OT offerings: Lev 2:11, 13. [In Num. 18 the connection is more remote.]
Every grain offering you bring to the LORD must be made without yeast, for you are not to burn any yeast or honey in an offering made to the LORD by fire. 13 Season all your grain offerings with salt. Do not leave the salt of the covenant of your God out of your grain offerings; add salt to all your offerings.
Note especially the last phrase of Lev 2:13, “add salt to all your offerings.” The association of an offering by fire in connection with salt is the only feasible intertextual reference that can explain Jesus’ statement in Mark 9:49. The later textual addition of “and every sacrifice shall be salted with salt” (in the Byz text) suggests that some copyists made this same connection.
If these are the correct connections (the discipleship theme in Mark 9 and the verbal allusion to Lev 2), then Jesus’ saying may be understood along these lines: under the old covenant sacrifices made by fire were to be salted. In the coming aegis of the new covenant, Jesus’ disciples are themselves are to become an offering by following and worshipping Jesus—and that offering is to be as complete and permanent as was the offering by fire under the old covenant. (Once it was salted and burned, it could not be “retrieved”!) If that is what Jesus meant in v. 39, then it is a conceptual parallel with Paul’s exhortation in Romans 12:1,
Therefore, I urge you, brothers, in view of God’s mercy, to offer your bodies as living sacrifices, holy and pleasing to God—this is your spiritual act of worship.
Jesus’ statement was metaphorical, but one which an observant, old covenant Jew would understand (and much more readily perhaps than we do today); Paul’s equivalent statement was non-metaphorical.
(The above is part one of what may be three parts over the next week or so. It is a summary of my SS lesson this morning with the adult class at Northmoreland. BTW, the most helpful discussion of these verses in the commentaries is France’s NIGTC vol.)