Christian Bale spent a lot of time studying the Scriptures in preparation for his role in Ridley Scott's upcoming biblical epic.

The "Exodus: Gods and Kings" actor plays Moses opposite Joel Edgerton, who stars as Rhamses.

The film tackles the deliverance of the Israelites from Egyptian slavery and their journey across the Red Sea. Bale undertook extensive research into the historical account, and especially on the figure of Moses.

His studies included pouring over works like Jonathan Kirsch's Moses, A Life, the Koran, and the Bible, and after, Bale admitted "realising [he] had no idea about Moses at all and how complex a character he was".

"Really, the question was what do we have to give up, because it's so fascinating ... you read the Torah from beginning to end [and] there is so much I had no idea about," Bale told The Christian Post.

"Moses is a far more extreme, mercurial character. I think that's why the story has resonated with mankind for so long."

The Academy Award winning actor has spoken several times about Moses ahead of the film's release but he recently found himself at the centre of controversy over negative comments he made during a press conference in Los Angeles in September, in which he described Moses as "barbaric" and "schizophrenic".

The comments were not well-received and drew the criticism of Christians in particular. Now Bale has upgraded his description of the Old Testament figure, who he says possessed intelligence and a strong will.

"If you read passages in the Bible, [Moses] objects to it, he says I'm not the right man, it's not for me, but I think he has such a vivid and intensely clear experience that it's something he just cannot shake ... his life will never be the same again," Bale said. "He was an intelligent enough man to have self-doubt."

In line with this, Bale tells viewers to expect a Moses "who wasn't supremely confident and was full of self-doubt."

'Exodus: Gods and Kings' is due out in US theatres on December 12.