The first occurrence.
And YHVH said to Gideon, “The people are yet too many; bring them down to the water, and I will try them for you there: and it shall be, that whoever I say to you, ‘He shall go with you,’ the same shall go with you; and whoever I say to you, ‘He shall not go with you,’ the same shall not go.” Jud 7:4
(Scripture picture: Every word of God is pure; He is a shielf to them that put their trust in Him. Pro 30:5)
The primitive root.
Strong’s H6884 צרף tsaraph a primitive root meaning, “to smelt a metal,” that is, to purge gold or silver (of the dross which is bonded in the ore) by fire. The 3-letter root is tsadey + resh + pey.
tsadey צ, ץ = the trail, thus a man concealed, journey, chase, hunt
resh ר = the head of man, thus head, first, top, beginning, man
pey פ, ף = the mouth, thus open, blow, scatter, edge
The story: To cause that which is concealed (tsadey) to rise to the top or surface (resh), so that it may be blown away or dispersed (pey).