What does of time and say which grain will from Macbeth mean?

The phrase "of time and say which grain will" in Macbeth means to predict the future and determine which course of action will be most successful. Macbeth, the protagonist of the play, utters these words as he struggles to decide whether to take action against King Duncan, the current ruler of Scotland. Macbeth is tempted by the prophecies of the witches, who have told him that he will one day be king, but he is also aware of the potential consequences of his actions. By wondering which "grain" of time to choose, Macbeth is wrestling with the choice between taking a proactive role in shaping his own destiny or allowing events to unfold without his interference. In other words, he is pondering which course of action he should take based on the timing and circumstances to ensure a positive outcome. Throughout the play, Macbeth is haunted by uncertainty and doubt as he makes decisions that ultimately lead to his downfall, suggesting that even when we attempt to control our destiny, fate may have other plans in store.