What does it mean in Luke 12 that says guard yourselves from the yeast that puffs up the Pharisees? Does this have any connection to the Old Testament when it says you can’t offer up yeast as an offering to god?
What does it mean? To find out for yourself, search a concordance, Bible software or blueletterbible.com you will find that puffs up -[KJV puffeth up] is used several times. In blueletterbible.com, you can click on Strong’s button near the middle and top of the page to turn on the Strong’s concordance number of each translated word.
[1 Corinthians 8:1 KJV] 1… Knowledge puffeth up, but charity edifieth.
after you turn on the Strong’s number, the verse will look like this:
[1 Corinthians 8:1 KJV] … Knowledge[G1108] puffeth up,[G5448] but[G1161] charity[G26] edifieth.[G3618]
In this case, puffeth up is the translation for the Greek word numbered 5448.
Check the Strong’s number of the translated word. In this case they are all the same: [G5448] Read through all of the verses using that phrase for that translated word to try to get a sense of the word.
From this, you may get the sense that “puffs up” makes one full of pride, or, we might say, full of hot air, like a balloon. It looks big and impressive, but in reality, like a popped balloon, there is little if any substance to it.
Then click on the Strong’s number to go to the page that gives more detailed information about that word.
Here we find the definition also includes “to make natural, to cause a thing to pass into nature”. This is similar to the flesh / carnal / natural versus spiritual mentioned primarily in Romans and 1 Corinthians.
Based on this, the Pharisees had turned that which was spiritual and full of His wisdom and substance, into that which was natural, full of hot air, pride, and no real importance.
How do we guard ourselves from this tendency? I have found Romans 1:21 to be a key verse for this. When I acknowledge Him in my life and thank Him, I turn from my own importance and recognize my utter dependence on Him and the gifts He has given me, which include the breath I just breathed. I remember that I am dust, molded into His image, into which He chose to impart His breath. For me, these are effective antidotes for being puffed up with nothing of substance, just ‘full of hot air’, focused on the natural which will pass rather than the spiritual which is eternal.
Yes, this connection does go back to the OT. It is the reason yeast is carefully cleaned from the house prior to Passover and the feast of unleavened bread. It is to encourage one to not only clean their physical house, but their spiritual house of all that is not of Him, as well.
Here is a little help on your question. By the way your question lead to another interesting topic. The covenant of salt. I have included some info in this post.
The fermentation process may have been connected with death; as such, it could not be associated with the altar, where sacrifices were given to the life-giver—God. Greek and Jewish sources from the ancient world attest to the symbolic connection made between leaven and corruption. The NT and rabbinic literature use leaven as a metaphor for sin and moral decay (e.g., 1 Cor 5:8; the rabbinic work Babylonian Talmud Berakhot 17a). While Israelites in general were not prohibited from consuming beverages that involved fermentation—such as wine—priests serving in the tabernacle were forbidden to drink them (Lev 10:9) upon penalty of death.
Barry, J. D., Mangum, D., Brown, D. R., Heiser, M. S., Custis, M., Ritzema, E., … Bomar, D. (2012, 2016). Faithlife Study Bible (Le 2:11). Bellingham, WA: Lexham Press.
And now to the salt.
COVENANT OF SALT [Heb. berîṯ melaḥ; Gk. diathḗkē halós]. As salt was regarded as a necessary ingredient of the daily food, and so of all sacrifices offered to Yahweh (Lev. 2:13), it became an easy step to the very close connection between salt and covenant-making. When men ate together they became friends. Cf. the Arabic expressions, “There is salt between us”; “He has eaten of my salt,” which means partaking of hospitality which cemented friendship; cf. “eat the salt of the palace” (Ezr. 4:14). Covenants were generally confirmed by sacrificial meals and salt was always present. Since, too, salt is a preservative, it would easily become symbolic of an enduring covenant. So offerings to Yahweh were to be by a statute forever, “a covenant of salt for ever before the Lord” (Nu. 18:19). David received his kingdom forever from the Lord by a “covenant of salt” (2 Ch. 13:5). In the light of these conceptions the remark of Our Lord becomes the more significant: “Have salt in yourselves, and be at peace with one another” (Mk. 9:50).
E. B. POLLARD
Pollard, E. B. (1979–1988). Covenant of Salt. In G. W. Bromiley (Ed.), The International Standard Bible Encyclopedia, Revised (Vol. 1, p. 794). Wm. B. Eerdmans.