Or HaChaim on Numbers 14:20/אור החיים על במדבר י״ד:כ׳

1 ויאמר ה׳ סלחתי כדברך, G'd said: "I have forgiven according to your word." G'd meant that He had not forgiven the sin absolutely, only, -as Moses had asked- that He would not kill them as one man. This was in response to Moses' argument that otherwise G'd would be perceived as unable to conquer the Canaanites. At any rate, He would invoke His attribute of ארך אפים by spreading the punishment over 40 years. The following verses are all illustrations of what G'd meant by invoking His attribute of ארך אפים on the one hand, and swearing an oath that all of the people would suffer retribution on the other.

2Another meaning of the word כדברך could be that G'd responded only because of Moses' having pleaded on behalf of the people, as well as the fact that one of Moses' arguments had been the presumed reaction of the Gentile nations if G'd were to wipe out the people all at once. We have already explained that Moses described the Gentiles' reaction as being either that G'd had ceased to be powerful, or that His powers sufficed only to overcome the Egyptians, not the more powerful Canaanites. G'd said (verse 23) ואולם חי אני, "in fact I am very much alive," in response to the Gentiles who would presume G'd to have faded away. Concerning the alternative reaction by the Gentiles that G'd did not have the power to disinherit the Canaanites, He said וימלא כבוד ה׳ את כל הארץ, that at the end of the period of retribution for this sinful generation He would demonstrate to one and all that He did have the power to carry out what He had said, that the seven Canaanite nations would be wiped out. G'd based His alternative plan of retribution and a degree of pardon for the Jewish people only on the honour He wished to bestow on Moses whose pleas He did not want to be perceived as having been rejected.