It is impossible to speak positively about the origin of this vestment. Medieval liturgists, e.g. Rupert of Deutz, favoured the view that the Christian vestments in general were derived from those of the Jewish priesthood, and that the alb in particular represents the Kethonet, a white linen tunic of which we read in Exodus 28:39. But a white linen tunic also formed part of the ordinary attire of both Romans and Greeks under the Empire. The fact that a white linen tunic was a common feature of secular attire also makes it difficult to determine the epoch to which we must assign the introduction of our present alb as a distinctly liturgical garment. The word alba, indeed, meets us not infrequently in connection with ecclesiastical vesture in the first seven centuries.
In the early centuries some sort of special white tunic was generally worn by priests under the chasuble, and that in course of time this came to be regarded as liturgical. A prayer mentioning "the tunic of chastity," which is assigned to the priest in the Stowe Missal, helps to confirm this view. Before the time of Rabanus Maurus, who wrote his "De Clericorum Institutione" in 818, the alb had become an integral part of the priest's sacrificial attire. Rabanus describes it fully (P.L., CVII, 306). It was to be put on after the amice. It was made, he says, of white linen, to symbolize the self-denial and chastity befitting a priest. It hung down to the ankles, to remind him that he was bound to practice good works to his life's end. At present the priest in putting on the alb says this prayer: "Purify me, O Lord, from all stain, and cleanse my heart, that washed in the Blood of the Lamb I may enjoy eternal delights."
Much greater diversity has been shown in the ornamentation of the alb. In the early ages we find the lower edge decorated with a border sometimes both rich and deep. Similar embroideries adorned the wrists and the caputium (head opening), i.e. the neck. The use of lace, though permitted, ought never to lose the character of a pure decoration. Albs, with lace reaching above the knees, are not, strictly speaking, en règle, though there is a special decree of 16 June, 1893, tolerating albs with lace below the cincture for canons at Mass, on solemn feast days. Formerly a decree of the Congregation of Rites prohibited any coloured lining behind the flounce, or cuffs, or lace with which the alb might be decorated, but a more recent decree (12 July, 1892) sanctioned the practice. In point of material the alb must be made of linen (woven of flax or hemp); hence cotton or wool are forbidden. The colour must now be white. Moreover, the use of silk and colours instead of albs of white linen has lasted on in isolated instances, both in East and West, down to our own days. It may be added that, like other sacerdotal vestments, the alb needs to be blessed before use.