Omnes populi, qui legibus et moribus reguntur, partim suo proprio, partim communi omnium hominum iure utuntur. (All peoples who are ruled by laws and long-standing custom partly use their own laws and partly the law that is common to all men)

Dig.1.1.10.2  Ulpianus 1 reg.

Iuris prudentia est divinarum atque humanarum rerum notitia, iusti atque iniusti scientia. (Learning and understanding of law demands that one study the human and divine and that one have knowledge of the what is just and unjust).

Dig.1.1.10pr. Ulpianus 1 reg.

Iustitia est constans et perpetua voluntas ius suum cuique tribuendi  (Justice is the constant and perpetual will of giving to everyone their Ius).

Gratian

Dig.1.1.11 Paulus 14 ad sab.

Ius pluribus modis dicitur: uno modo, cum id quod semper aequum ac bonum est ius dicitur, ut est ius naturale. (The word "ius" can be understood in several ways: in one way ius is that which is always fair and good, such as natural law).

Mosaic of Justinian, San Vitale, Ravenna

Dig.1.1.10.1   Ulpianus 1 reg.

Iuris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere

(The basic principles of ius are: to live honestly, not to harm other people, and to recognize the rights of others).