7918. And ye shall take a bunch of hyssop. That this signifies an external means by which there is purification, is evident from the signification of "hyssop," as being external truth, which is a means of purification (of which in what follows). It is said that they should "take a bunch of hyssop," because "a bunch" is predicated of truths and their arrangement (n. 5530, 5881, 7408). That "hyssop" denotes external truth as a means of purification, is because all spiritual purification is effected by means of truths. For the earthly and worldly loves from which man is to be purified, are not recognized except by means of truths, and when these are instilled by the Lord, there is also instilled at the same time horror for these loves as for things unclean and damnable, the effect of which is that when anything of the kind flows into the thought, this feeling of horror returns, and consequently aversion for such things. Thus man is purified by truths as by an external means. It was on this account ordered that circumcision should be performed by means of knives or lancets of flint. (That "lancets" or "knives of flint" denote the truths of faith whereby purification is effected, see n. 2799, 7044; and that "circumcision" denotes purification from filthy loves, n. 2039, 2632, 3112, 3413, 4462, 7045.)
 As "hyssop" has this signification, it was therefore employed in cleansings, which in the internal sense signified purifications from falsities and evils, as in the cleansing of the leprosy, in Moses:
The priest shall take for the leper that is to be cleansed two living clean birds, and cedar wood, and scarlet and hyssop, and shall dip them in the blood of the bird that was killed, and he shall sprinkle upon him that is to be cleansed (Lev. 14:4-7);
and in like manner "in the cleansing of a house, if the leprosy be in it" (verses 49-51). For preparing the water of separation by which cleansings were wrought, cedar wood and hyssop were also employed (Num. 19:6, 18); by "cedar wood" was signified internal spiritual truth, and by "hyssop" external; thus by "cedar" an interior means of purification, by "hyssop" an exterior one. That "hyssop" denotes a means of purification is very manifest in David:
Thou shalt purge me with hyssop, and I shall become clean; Thou shalt wash me, and I shall be whiter than snow (Ps. 51:7);
where "to be purged with hyssop and made clean" denotes external purification; "to be washed and made whiter than snow," internal purification; "snow" and "whiteness" are predicated of truth (n. 3301, 3993, 4007, 5319). That "hyssop" denotes lowest truth, and "cedar" highest truth, is plain from these words in the first book of Kings:
Solomon spoke of woods, from the cedar which is in Lebanon even unto the hyssop that goeth out of the wall (1 Kings 4:33);
where "cedar" denotes internal truth which is of intelligence; and "hyssop," external truth which is of intelligence.