The General Agrippas asked Rabban Gamliel, “It is written in your Torah, ‘For the Lord thy God is a devouring fire, a jealous God (El kanna)’ (Sefer 4:24). Is a wise man jealous of any but a wise man, a warrior of any but a warrior, a rich man of any but a rich man?” Rabban Gamliel replied, “I will give you a parable: To what is this similar? To a man who marries an additional wife. If the second wife is her superior, the first will not be jealous of her, but if she is her inferior, the first wife will be jealous of her.”
The Maharsha explains that General Agrippas understood the term kanna to mean jealousy, as a man is jealous of his friend, meaning that he desires to have his friend’s possessions, status or honor. This understanding led him to ask how God could possibly be jealous of pagan idols who, according to Jewish tradition, are valueless and without standing. Rabban Gamliel responded by means of his parable that the term kanna in this context does not mean jealousy. Just as the senior wife would not be jealous of the new woman who has entered the household if she is of lower social class, so, too, God cannot possibly be jealous of a false god. Rather, the term kanna connotes anger, that the first wife is angry at her husband for bringing into their household a woman of low class to replace her.
Similarly, God is an El kanna – he is angry at the Jewish People when they choose to abandon Him and exchange Him for pagan idols, which are so insignificant in comparison to Him.