In the Southern and Northern Dynasties(420-589), in the reign of king Wu of Liang, there was a monk called Master Yun Guang who was a very accomplished(有技巧的) preacher.

Once he explained the sutra(佛经，箴言) so proformdly and subtly that the God of Flowers was moved and sent divine(神圣的) flowers down to earth.

Soon the land was covered with flowers.

南朝梁国的开国皇帝梁武帝萧衍特别笃信佛教，他请云光法师宣讲佛法，在讲 涅槃经　时，梁武帝从早到晚认真听讲，没有丝毫倦意。

云光法师说得绘声绘色，竟感动了上天，香花从空中纷纷落下。

梁武帝从此更加信佛，后来干脆出家。

This idiom was later used metaphorically to describe talking in a vivid and eloquent way(mostly in an exaggerated and impartical manner).

传说梁武帝时有个和尚讲经，感动了上天，天上纷纷落下花来。

形容说话有声有色，极其动听(多指夸张而不符合实际)。

【中国成语故事中英对照 天花乱坠查看网站：[db:时间]】