Commentary on the verse, “Then woe to those who write the Book with their own hands and then say, “This is from Allaah,” to purchase with it a little price! Woe to them for what their hands have written and woe to them for that they earn thereby” [al-Baqarah 2:79]

I have a question about this verse:
2:79 Then woe to those who write the Book with their own hands, and then say:"This is from Allah," to traffic with it for miserable price!- Woe to them for what their hands do write, and for the gain they make thereby.
What is it that they used to gain by changing the books after they were revealed? Did they literally "sell" these changed books to people and make a profit off of them?.

Praise be to Allaah.

In this verse, Allah warns those who distort the Book and change laws, those who betrayed the trust of knowledge and religion, with loss, punishment and doom on the Day of Resurrection. They distorted the Book by adding and subtracting, and they said that this was from Allah, lying and fabricating. Their aim in distorting the Book was to make transient worldly gains. This is represented in a number of things: 

1.

Worldly status by holding onto the leading positions which were enjoyed by the prominent figures and rabbis of the Jews. They knew that if they believed and submitted and accepted the leadership of the new Prophet, they would lose their position that made them look down on people, and their followers would turn away from them to follow the new Prophet, so they erased everything from their Books that foretold the coming of Muhammad (blessings and peace of Allah be upon him) and they concealed what knowledge they had of this matter. Thus they bought transient worldly gain at the cost of the eternal Hereafter. 

Al-Baghawi (may Allah have mercy on him) said: 

That is because the rabbis of the Jews were afraid of losing their livelihood and position of leadership, when the Prophet (blessings and peace of Allah be upon him) came to Madeenah. So they tried to prevent the Jews from believing in him. They went to his description in the Torah, where he is described as having a handsome face, with handsome hair, kohl-rimmed eyes and being of average height, and they changed it, writing instead: Tall, blue, with straight hair. When their foolish ones asked them about the description of the Prophet, they read what they had written and said that he was different from this description, so they disbelieved him and rejected him. So Allah said (interpretation of the meaning): “Then woe to those who write the Book with their own hands” [al-Baqarah 2:79]. End quote. 

Ma‘aalim al-Tanzeel, 1/115 

Al-Qurtubi (may Allah have mercy on him) said: 

Ibn Ishaaq and al-Kalbi said: The description of the Messenger of Allah (blessings and peace of Allah be upon him) in their Book said that he was of average height and white, but they changed it to say that he was dark with long, straight hair, and they said to their companions and followers: Look at the description of the Prophet (blessings and peace of Allah be upon him) who will be sent at the end of time; he does not resemble this one. The rabbis and scholars held leadership positions and had an income and they were afraid that if they spoke the truth they would lose their livelihood and positions of leadership, so they changed it. End quote. 

Al-Jaami‘ li Ahkaam al-Qur’aan 

2.

This little price was in return for what they wrote of pages of books. Some of the priests and rabbis of the People of the Book wrote it themselves in order to sell it to some ignorant people and earn money from that. Because of their stinginess and treachery, they deceived them about the word of Allah, may He be glorified and exalted, and they said that these books were from Allah when they are not from Allah. 

Qataadah (may Allah have mercy on him) said: 

Some people among the Children of Israel wrote a book with their own hands so as to earn a living from people, and they said: This is from Allah, but it is not from Allah. End quote. 

Al-Saddi (may Allah have mercy on him) said: 

Some of the Jews wrote a book themselves to sell to the Arabs, and they told them that it was from Allah, so that they could take a little price for it. End quote. 

Jaami‘ al-Bayaan, 2/270-271 

Al-‘Allaamah al-Taahir ibn ‘Ashoor (may Allah have mercy on him) mentioned two other aspects of the worldly greed that led some of the People of the Book to distort their Books. He (may Allah have mercy on him) said:  

The price meant here is pleasing the common folk, by changing the rulings of the religion for them so that they will be in accordance with their whims and desires, or to claim that they have knowledge even though they are ignorant. So they fabricated worthless books full of stories and simple information so as to pretend that they had knowledge in front of people because they were unable to grasp true knowledge, and they wanted prominence and false leadership. So they fabricated stories and ideas in which there is no true knowledge at all, then they propagated it and attributed it to Allah and His Religion. This is the attitude of the ignorant who seek leadership without being qualified for it, so that they may appear as scholars in the eyes of the common folk and those who cannot distinguish between true and false. End quote. 

Al-Tahreer wa’l-Tanweer, 1/577 

And Allah knows best.