Numbers 5:13

וְשָׁכַ֨ב אִ֣ישׁ אֹתָהּ֮ שִׁכְבַת־זֶרַע֒ וְנֶעְלַם֙ מֵעֵינֵ֣י אִישָׁ֔הּ וְנִסְתְּרָ֖ה וְהִ֣יא נִטְמָ֑אָה וְעֵד֙ אֵ֣ין בָּ֔הּ וְהִ֖וא לֹ֥א נִתְפָּֽשָׂה׃

καὶ κοιμηθῇ τις μετ’ αὐτῆς κοίτην σπέρματος, καὶ λάθῃ ἐξ ὀφθαλμῶν τοῦ ἀνδρὸς αὐτῆς καὶ κρύψῃ, αὐτὴ δὲ ᾖ μεμιαμμένη, καὶ μάρτυς μὴ ἦν μετ’ αὐτῆς καὶ αὐτὴ μὴ ᾖ συνειλημμένη·

Greek text from Swete's edition, CC BY-SA 4.0

Que alguno se hubiere echado con ella en carnal ayuntamiento, y su marido no lo hubiese visto por haberse ella contaminado ocultamente, ni hubiere testigo contra ella, ni ella hubiere sido cogida en el acto;

by sleeping with another man, and it is concealed from her husband and her impurity is undetected (since there is no witness against her and she was not caught in the act),