Overall meaning : The Jews will never fight you, Muslims, in a body except from within fortified cities and from behind walls. Their enmity among themselves is very great indeed; you think them to be united, but their hearts are divided. That is because they are a people who have no sense!
The Jews of Banu An-Nadheer are just like those before them—the Jews of Banu Quraydhah and the Quraysh unbelievers—shortly before the expulsion of the Banu An-Nadheer Jews. They suffered punishment for their unbelief in this life, and a grievous punishment awaits them in the next.
Those hypocrites—who let the Jews of Banu An-Nadheer down after having promised to go forth with them if they were expelled and to aid them if they were fought against—are just like Satan, who says to man, ‘Disbelieve in Allah.’ Then as soon as he does so, Satan disowns him and lets him down, saying, ‘I fear Allah, the Lord of all the worlds!’ Consequently, they will both end up in the Fire, in which they will abide for ever. Thus will the wrongdoers be repaid.