Why did He have compassion not to destroy them?
Radak: I left their children, to bring them to the land.
Malbim: Even though He swore not to bring them to Eretz Yisrael, He did not kill them immediately, for this would wipe out the nation. Chas is compassion on something that he needs. Before it said that He did not destroy them due to honor of His name. Now it says that since the sin was due to heresy and lack of Emunah, He saw 1 that if He delays them 40 years in the Midbar, and they see the constant miracles and Hashgachah, they will recognize Hashem - "Atem Re'isem Es Kol Asher Asah Hashem l'Eineichem b'Eretz Egypt; ... v'Lo Nasan Hashem Lachem Lev La'da'as...; va'Olech Eschem Arba'im Shanah ba'Midbar; ... Lema'an Ted'u Ki Ani Hashem Elokeichem" (Devarim 29:1, 3-5). One understands his Rebbi's intent only after 40 years (Avodah Zarah 5b).
Hashem's knowledge does not change! Perhaps Malbim means that now, according to Yedi'ah Sichlis, they are proper to repent if they will see... Ohr Yisrael (Igeres 30) says that 'Osim Teshuvah' depends on Yedi'ah Sichlis; then, He waits for a sinner to repent. (PF)
