Justinian established  a ten-man commission chaired by John the Cappadocian to produce a new code of law. The commission produced the Codex Justinianus (Codex vetus) on 7 April, 529.  Then Justinian ordered the codification of  the legal opinions of the Roman jurists from ca. first century B.C. to the third century A.D.  On 15 December 530 he  ordered a commission to work at it: sixteen lawyers from the legal fraternities of Constantinople and Beirut, men headed by Tribonian, who had already been a member of the commission that produced the Codex Justinianus. The result of their labor was published on 16 December, 533 and was called the Digest, or to give it its Greek name, the Pandects. At the same time, a committee also headed by Tribonian was working on a textbook for law students, the Institutes that was based in large part on an earlier work of the jurist Gaius.  It was published  on 16 November. One byproduct of all this labor was to make the Codex vetus obsolete, and hence a new edition was published on 16 November, 534 and the first edition has failed to survive. This body of legal achievement has been known since the sixteenth century as the Corpus iuris civilis and it was intended as a unified body of law. Justinian forbade commentaries on the Digest and probably the rule applied to the whole Corpus. The last part of Justinian's codification was the Novels (Novellae)  They were new laws that he issued after the Corpus was published.  The language of these constitutions was Greek.   He may  have planned a collection of his own legislation, but they were only put together as a collection until after his death.

Mosaic of Justinian in San Vitale, Ravenna