Rashi on Leviticus 4:22/רש"י על ויקרא ד׳:כ״ב

1אשר נשיא יחטא — The word אשר is connected in meaning with ‎‎‏אשרי “happy”. Happy is the generation whose prince (king) takes care to bring an atonement sacrifice even for an inadvertent act of his; how much the more certain is it that he will do penance for his wilful sins (Sifra, Vayikra Dibbura d'Chovah, Section 5 1; Horayot 10b)