ל֥וּ חָכְמ֖וּ יַשְׂכִּ֣ילוּ זֹ֑את יָבִ֖ינוּ לְאַחֲרִיתָֽם׃
If they were wise, they would understand this, They would discern their latter end.
Rashi on Deuteronomy
יבינו לאחריתם THEY WOULD CONSIDER THEIR LATTER END — i.e. they would set their heart to comprehend the ultimate reason for the misfortune of the Israelites,
Sforno on Deuteronomy
לו חכמו ישכילו זאת, how the Israelites could have fallen into their hands, something that is completely unnatural, could only have been due as punishment for their sins.
Rashbam on Deuteronomy
לו חכמו, if these gentile nations had possessed any real intelligence they would have said: איכה ירדוף אחד, how was it ever possible that a single one of us could successfully pursue אלף, a thousand Jews, something they used to be able to do to us. This could only be accounted for by the fact that their G’d, צורם, had sold them out. This was the result of their offending Him by their sins. The word צור as simile for G’d has already occurred in verse 4 of this chapter.