To skeptics, Numbers 15:24-28 seem to say that sacrifices can, in at least some cases, take away sin, which contradicts Heb. 10:11: “sacrifices…can never take away sins.” Scripture states that the Old Testament sacrifices could never make the person offering them “perfect” (see Heb. 7:19). Each time Israel sinned, they would have to make further atonement (see Heb. 9:9). However, when God provided His own sacrificial Lamb (Jesus of Nazareth), Jesus’ death on the cross accomplished what the sacrificial system could not do. It made the believer perfect in the sight of God. (See Heb. 10:9–14.)
The Numbers passage does not say that sacrifices can “take away sin,” just that God offered temporary forgiveness through the sacrificial system. Humanity’s sin debt wasn’t “paid in full” until Jesus shed His blood in payment. It’s like the difference between accepting a check as payment, and actually cashing the check and receiving the funds. There is no contradiction.
Numbers 15:24 then it will be, if it is unintentionally committed, without the knowledge of the congregation, that the whole congregation shall offer one young bull as a burnt offering, as a sweet aroma to the Lord, with its grain offering and its drink offering, according to the ordinance, and one kid of the goats as a sin offering.25 So the priest shall make atonement for the whole congregation of the children of Israel, and it shall be forgiven them, for it was unintentional; they shall bring their offering, an offering made by fire to the Lord, and their sin offering before the Lord, for their unintended sin.26 It shall be forgiven the whole congregation of the children of Israel and the stranger who dwells among them, because all the people did it unintentionally.27 ‘And if a person sins unintentionally, then he shall bring a female goat in its first year as a sin offering.28 So the priest shall make atonement for the person who sins unintentionally, when he sins unintentionally before the Lord, to make atonement for him; and it shall be forgiven him.