שמואל ב כ:יט פירוש: רש״י

I am [from the people of the city] that are loyal and trustworthy to Yisroel. I am from the people of the city that are loyal and trustworthy to Yisroel and to the king. An Aggadic Midrash [states:] this was Serach, the daughter of Asher. I faithfully rewarded those who faithful [to God]: Through me, the location of Yosef's coffin was revealed to Moshe. I told Yakov that Yosef was alive.