MEN THAT ARE LIKE WELL-FED LUSTY STALLIONS:

“When I had fed them to the full, Then they committed adultery And assembled themselves by troops in the harlots' houses. They were like well-fed lusty stallions; Every one neighed after his neighbor's wife. Shall I not punish them for these things?" says the LORD. "And shall I not avenge Myself on such a nation as this? Jer. 5: 7-9

God says, the adulterers are like well-fed lusty stallions. Whenever they wake up in the morning, the first thing they think of is WINE and SEX. “In the morning” is a phrase for unceasing eagerness in any pursuit; such was the men avidity after loosed women. They wake up in the morning and continually wander to and fro, inflamed with lust seeking for the next prey. Some of them even enter into the temple of God and lewd innocent girls or widows promising to marry them, but only to defile and abandoned them.

Why did God compare such men to a stallion? Stallions are male Horses known for their powerful sexual proclivity and mindless obedience to their instincts; they are very strong, sexually active and can’t restrain themselves when they sighted a female. Once stallions sighted a Mare, they become insane with lust until they have sex with her. Verse 8 says, “Every one neighed after his neighbour's wife” like the Stallions. Neigh is from the Hebrew tsahal, "to cry aloud”: Figuratively used to indicate lustful desire. Neighing is the whinnying sounds a male horse makes when he desires a female. 

God is saying that these men are lusting after women who are not their wives as a stallion neighing over a Mare (female animals). In such manner, some men pursued their promiscuity. They even use drugs to be extra strong so they can have multiple ejaculations like Stallions. 

Another example of a Stallion craving for sex was Judah in Genesis 38:15, who was a great disgrace to God that he hastily desired intercourse with an unknown woman whom he saw from afar. He was now old; and therefore age alone, even in a lascivious man, ought to have restrained the fervour of intemperance. He sees the woman at a distance, and it is not possible that he should have been captivated by her beauty. The lust kindles him as a stallion neighs when it smells a mare. He is therefore set before us as an example, that we may learn how easily the lust of the flesh would break forth, and causes us to precipitate into fornication; let us mark, that the dishonour which Judah sustained in consequence of his incest, was a punishment divinely inflicted upon him. 

Culled from my book manuscript "The Neighbour's Wife".