The Talmud in Sanhedrin (21b) states: Rava says, even if one were to inherit from his ancestors a Torah scroll it is still incumbent upon him to write a Sefer Torah or have one written for him. The Talmud bases its statement upon the above posuk which mandates the writing of a Sefer Torah. The Rambam and various other codifiers of halacha maintain this statement. There are many reasons given for the imperative to have a personal Torah written. The Sefer Hachinuch states that the reason for this mitzvah is to increase the number of Torah scrolls and, for that matter, volumes of various religious books. This is so that we should be able to lend them to any person who does not have ready access to seforim. He indicates the necessity for a Jew to read from new books, for fear that he may become loathe to read from old scrolls that were worn and difficult to decipher. He explains that it was the custom for many a noble and a G-d-fearing Jew to establish in his home a scriptorium for scribes to come and write volumes of religious texts.
The Darchei Mussar suggests that we learn from this mitzvah that one should not study Torah and perform mitzvos only because it was handed down to him from his ancestors. Indeed, Chazal say about the Torah :“Every day they shall be for you as new“. Torah does not tolerate complacency. It must be studied with renewed vigor and vitality every day. This is the Torah‘s imperative; even though you are studying the same Torah which has been studied for generations, your attitude should be one of newness and novelty as if it was recently transmitted directly to you on Mount Sinai.