'Illegitimate' in the Bible

And Aaron's sons Nadab and Abihu each took his censer, and they put fire in them and placed incense on it; then they presented {before} Yahweh illegitimate fire, which he had not commanded them.

An illegitimate child may not come into the assembly of Yahweh; even [to] the tenth generation none {of his descendants} may come into the assembly of Yahweh.

They have dealt faithlessly with Yahweh because they have borne illegitimate children. Now [the] new moon will devour them with their fields.