Presently we are in the midst of a study of the seven bowls of wrath in Revelation 16. The third angel poured out his bowl of wrath from God upon the rivers and the fountains of waters (Revelation 16:4), and the wrath of God turned the waters into blood. It may be that Revelation 16:5-7 is a summary of the first three bowl judgments. What occurs here is the angel of the waters speaks out and declares the Lord righteous for his judgment (Revelation 16:5). The reason he offers for his declaration is that they (i.e. the earth and the sea and the fountains of waters, which include the rivers that form from the flow of the fountains) **they** have shed the blood of the saints and the prophets. Therefore, i.e. because of the blood guilt of the earth, the sea, and the fountains of waters, the Lord gave them blood to drink (Revelation 16:6).
Then, another voice came out from the altar in a kind of “two witness” agreement that validated the declaration that the Lord’s judgments were righteous (Revelation 16:7), and the altar is connected with the blood of the saints (Revelation 6:9-11). What I find interesting at this point is that Jesus, just before he was crucified, declared that the Jewish authorities were guilty of shedding the blood of all the righteous recorded in Scripture, and would further expose their blood guilt by persecuting and killing all those he (the Lord) would send to them (Matthew 23:29-36).
What did John mean by the fountains or springs of waters? First of all, we need to keep in mind that the Fountain of Living Waters is the Lord (Jeremiah 2:13; 17:13). He is the Fountain or Source of all that is good. He is the Creator of all things and the Giver of all life. Nevertheless, the fountains of waters that are mentioned in Revelation 16:4 have nothing to do with the Lord or life or anything we might call good. Rather, the wrath of God is poured out upon them. While the term, fountain of living waters, has to do with having eternal life (Psalm 36:9; Revelation 21:6), it seems that the fountains of waters in Revelation 16:4 promise life, but, for whatever reason they are unable to deliver on the promises they make. Moreover, the verb in the Greek is in the singular. So, whatever the rivers and the fountains (both plural) of waters refer to in this text, they are taken together as though they described one entity, and **it** (not they) became blood (Revelation 16:4).
I find it interesting that Jeremiah 2:13, which identifies the Lord as the Fountain of Living Waters, also claims that in rejecting him the people have chosen cisterns, which collect rain water to sustain life, but these cisterns are broken and are unable to retain any life giving water at all! In other words, they are unable to fulfill their promise of life. The Scriptures liken a fountain to ‘understanding’ (Proverbs 16:22) and the Law (Proverbs 13:14). So, it seems that the fountains of Revelation 16:4 concern a source of teachings or doctrines about how to live. Yet, in the context of a broken cistern, that source or religion, if you will, is false and unable to deliver on its promises. The Scriptures further liken a man’s mouth to a fountain (James 3:10-11), and then they compare the false teacher (2Peter 2:1) to a well (a spring, or a fountain) without water (2Peter 2:17). Moreover, Jerusalem as a source of wickedness and violence is referred to as a fountain (Jeremiah 6:6-7), and the persecution of the righteous a troubled fountain (Proverbs 25:26).
It is in this context, then, that we should understand the angel pouring out his bowl of wrath upon the rivers and fountains of waters (Revelation 16:4). The Lord is angry with those who shed the blood of the righteous (Revelation 16:6), and Jeremiah identifies the fountain as Jerusalem (Jeremiah 6:6-7) to which the Lord agrees (Matthew 23:29-36). So, at long last, the Lord judges Jerusalem according to his own righteousness (Revelation 16:5, 7) by giving her false prophets to guide the Jewish state, so their wickedness would be brought to its ultimate end (cf. Matthew 23:31-32).
 The next three judgments also seem to have a recap in Revelation 16:13-16.