פּירוש אויף שמואל ב 21:4

We are not interested in silver or gold from Shaul. We are only interested in [retribution against] people. He [Dovid] wanted to appease them with money but they did not want [to accept it]. He [Dovid] said, "It may be that they are embarrassed of each other." [Therefore] he went and tried to appease each one individually [but] they [still] would not be appeased. That is why it is written here, "I am not interested in silver or gold etc" in singular form.¹²The verse is written with לִי in singular form, but is read with לָנוּ, plural form indicating that Dovid tried to appease them both collectively as a group and also on an individual basis. This I saw in the Yerushalmi Talmud.¹³Sanhedrin 29a.

And we are interested in killing anyone. Among the rest of the Bnei Yisroel because they did not agrieve us.