Vayikra 22:18

Speak unto Aharon, and to his Banim, and unto kol Bnei Yisroel, and say unto them, Whatsoever he be of the Bais Yisroel, or of the Ger B'Yisroel, that will offer his korban for any of his nederim, and for all his nedavot, which they will offer unto HASHEM for an olah