The "midst" of something in the Bible represents the thing that is most central and most important to the spiritual state being described, the motivation that drives everything else. In general this will be something we love or feel, because at the core of things we are what we love; our loves define us.

(Референци: Apocalypse Revealed 44, 90, 268; Arcana Coelestia 2252, 2940, 10153, 10365, 10557, 10635, 10641)

7044. 'And Zipporah took a flint' means that the representative Church used truth to demonstrate the actual nature. This is clear from the representation of 'Zipporah' here as the representative Church; and from the meaning of 'a flint' as the truth of faith. The use of knives made of flint to carry out circumcision meant the use of the truths of faith to carry out purification from filthy kinds of love, 2039, 2046, 2799; for circumcision was an act that represented purification from those kinds of love, 2799. The reason why purification is effected by means of the truths of faith is that these truths teach what good is and also what evil is, and so what ought to be done and what ought not to be done. And when a person knows those truths and wishes to act in accordance with them, he is being led by the Lord and purified by the Divine means that are His. Since the truths of faith teach what evil is and what good is it is evident that 'Zipporah took a flint' means the use of truth to demonstrate the actual nature. The fact that 'Zipporah' represents the representative Church is clear from the things that follow in these verses.