How can we say that God is without sin when the Bible clearly describes Him as being given to jealousy (c.f., Ex 20:5)?
First we have to distinguish between jealousy and covetousness. We often use those words interchangeably, and the Bible also seems to treat them as synonyms on some occasions.
But not always. There is jealousy that is appropriate, for instance jealousy that is zeal for God (c.f., Num 25:11). But a better example would be Numbers 5:14 – jealousy for one’s spouse.
If I am jealous of another man’s wife, car, or house, that’s simply covetousness. But if I’m jealous of my wife – that is, if I think she’s given undo attention, or worse, to another man – that’s absolutely correct. In that case, something that is actually mine has been given to someone else.
It is in this sense that the Lord is a jealous God:
“Do not follow other gods, the gods of the peoples around you; for the LORD your God, who is among you, is a jealous God …” (Deut 6:14-15).
The same God who was jealous for His people Israel is jealous for His bride, the Church.
Whether His people turn to graven images or to modern idols – e.g., comfort, universalism, or church – God Almighty will not share what is rightfully His for very long.
The Lord is still “a consuming fire, a jealous God” (Deut 4:24).