In that day. At the time when the great mourning (Zechariah 12:1-14.) takes place, or, more generally, in the Messianic period, when all these things shall be fulfilled. Shall be a fountain opened, etc.
Shah be opened and continue open. The allusion is to the lustral rites practised in the consecration of the Levites, who were to have "water of sin" sprinkled on them, and to "the water of separation," or "water of uncleanness" (the word found in our passage), used for purposes of legal purification (see Numbers 8:7; Numbers 19:9).
Instead of this merely ceremonial cleansing, there should be in the Christian Church the cleansing of the soul by the blood of Christ (1 Peter 1:2; 1 John 1:7). Septuagint, ἔσται πᾶς τόπος διανοιγόμενος, "Every place shall he opened."
The house of David and the inhabitants of Jerusalem represent the whole nation, as in Zechariah 12:10; the cleansing is as universal as the sin (see the announcement in Ezekiel 36:25; Ezekiel 47:1-12; Joel 3:18).
For sin and for uncleanness. The latter word is used for the separation on account of uncleanness (Le 15:20, etc.); and the two terms together comprise all guilt and pollution.