According to Wikipedia article devoted to the tale Perceval, the Story of the Grail by Chrétien de Troyes,
Perceval is the earliest recorded account of what was to become the Quest for the Holy Grail but describes only a golden grail (a serving dish) in the central scene, does not call it "holy" and treats a lance, appearing at the same time, as equally significant.
However, I've been reading this romance in an Italian translation by Gabriella Agrati and Maria Letizia Magini and, at a certain point, when the hermit explains to Parceval that is the Fisher King’s father who uses the grail, he calls it with the Italian word "santo", which means "holy":
E sappi che il Re Pescatore è il figlio di quel re che si nutre del Santo Graal. Ma non credere che gli si serva luccio lampreda o salmone. Solo ostia gli si porta nel Santo Graal.
This is an extract from the book Chrétien de Troyes, I romanzi cortesi, edited by Mondadori (page 611 in the Kindle ebook with ISBN 9788852038693), that can more or less be translated this way:
And know that the Fisher King is the son of that king who feeds on the Holy Grail. But don't think that pike, lamprey or salmon is served to him. Only host is brought to him in the Holy Grail.
I've tried to access the Old French original, but this part of the text has not yet been included in the Wikisource project.
So, I wonder if the original text by Chrétien de Troyes calls the grail "holy" (that is, "saint" or an equivalent word in Old French) or not. That's my question.