Judges 14 :18

If ye had not ploughed with my heifer - If my wife had not been unfaithful to my bed, she would not have been unfaithful to my secret; and, you being her paramours, your interest was more precious to her than that of her husband. She has betrayed me through her attachment to you. Calmet has properly remarked, in quoting the Septuagint, that to plough with one's heifer, or to plough in another man's ground, are delicate turns of expression used both by the Greeks and Latins, as well as the Hebrews, to point out a wife's infidelities. Thus Theognis, Gnom. v. 581: -

Εχθαιρω δε γυναικα περιδρομον, ανδρα τε μαργον.

Ὁς την αλλονριην βουλετ' αρουραν αρουν.

"I detest a woman who gads about, and also a libidinous man, who wishes to plough in another man's ground."

Fundum alienium arat, incultum familiarem deserit.

Plautus.

"He ploughs another's farm, and leaves his own heritage uncultivated."

Milo domi non est, perepre at Milone profecto

Arva vacant, uxor non minus inde parit.

Martial.

"Milo is not at home, and Milo being from home, his field lies uncultivated; his wife, nevertheless, continues to breed, and brings forth children."

There is the same metaphor in the following lines of Virgil: -

Hoc faciunt, nimo ne luxu obtusior usus,

Sit genitali arvo, sulcosque oblimet inertes.

continued...

They try to give the answer in a way to make it appear that they had guessed it. Samson saw at once that she had betrayed him. He lets them know in a speech, which was of the nature of a riddle, that he had discovered the treachery.

14:18 If ye had not and c. - If you had not employed my wife to find it out, as men plough up the ground with an heifer, thereby discovering its hidden parts; he calls her heifer, because she was joined with him in the same yoke.