They must not put olive oil or incense on it, because it is a sin offering

 Leviticus 5:1-13

If anyone sins because they do not speak up when they hear a public charge to testify regarding something they have seen or learned about, they will be held responsible. If they touch human uncleanness. If anyone thoughtlessly takes an oath to do anything, whether good or evil. 

As a penalty for the sin they have committed, they must bring to the Lord a female lamb or goat from the flock as a sin offering[a]; and the priest shall make atonement for them for their sin.

Anyone who cannot afford a lamb is to bring two doves or two young pigeons to the Lord as a penalty for their sin—one for a sin offering and the other for a burnt offering.

If, however, they cannot afford two doves or two young pigeons, they are to bring as an offering for their sin a tenth of an ephah of the finest flour for a sin offering. They must not put olive oil or incense on it, because it is a sin offering. 

In this way the priest will make atonement for them for any of these sins they have committed, and they will be forgiven. The rest of the offering will belong to the priest, as in the case of the grain offering.

There was a standard pattern of ritual. Worshippers brought their offerings (physically perfect animals from the herd or flock, or in the case of the poor, doves or pigeons) to the forecourt of God's Tent. They laid their hand on their offering, indicating that it was their property and substitute, and slaughtered it. If is was a public offering the priest did this. The priest took the basin of blood and spattered part with certain portions of fat. The remainder was then eaten by the priests, or by the priests and their families, or by priests and worshippers together.

Why?

Adding oil or incense means a joyful matter, but the sin offering is guilt that prays to the Lord to erase this sin, which is not God's delight. So it has to clean and pure.

Sin offerings include the love of God, for depends on everyone's situation, they may devote the offering by their capability.

Roughly take an oath or touched unclean animal or human, or did not wit what is truth. All of these is sins.

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有人說是贖愆祭，是贖罪祭。

1.當為而不為，有聽見發誓，卻不說出來。明知卻不願意作證。這是罪，使法庭無法公義審判，違反神的原則。

2.冒失，輕忽、不謹慎。摸了不潔淨的東西，自己卻不知道，知道就是有罪，即使不知道仍然有罪。隨便發誓，卻不知道。不知道這樣發誓是冒失，隨便的。例如有人說大話，不能兌現。我們常說我要怎樣，怎樣卻不去做！ 我們因為軟弱可發生的事。基督徒在此特別容易犯！

處理方式： 1.認罪悔改 2.獻贖罪祭

贖愆祭和贖罪祭同樣是贖罪祭。這裏說的是一般人犯罪的事。

窮人不會因為沒有錢以致沒有辦法贖罪。救恩是給所有人的。

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How?

To be a Christian has to be honest and do everything with love and pure heart, God is my fortress and savior.