The fruit commonly associated with being forbidden in biblical times is the apple. This association primarily stems from the story of Adam and Eve in the Book of Genesis, where they ate from the "tree of the knowledge of good and evil," leading to their expulsion from the Garden of Eden. Although the Bible does not specify the type of fruit, artistic and literary interpretations over centuries have often depicted it as an apple, possibly due to its symbolism of temptation and knowledge. Thus, the apple has become a cultural icon representing forbidden knowledge throughout various traditions.