[God] answered: "O Noah, behold, he was not of thy family, for, verily, he was unrighteous in his conduct.68
And thou shalt not ask of Me anything whereof thou canst not have any knowledge:69
thus, behold, do I admonish thee lest thou become one of those who are unaware [of what is right]."70
According to some commentators (e.g., Tabari and Razi), the phrase innahu 'amal ghayr salih relates to Noah's prayer for his son, and constitutes a divine reproach - in which case it should be rendered as "verily, this [prayer] is unrighteous conduct [on thy part]". Others, however (e.g., Zamakhshari), reject this interpretation and relate the above phrase to the son, in the manner rendered by me. This, I believe, is more in tune with the statement, "he was not of thy family" - i.e., spiritually, inasmuch as he was of, or preferred to remain with, "those who deny the truth".
I.e., knowledge of the innermost reasons of God's decrees and of the ultimate destiny of any human being in the hereafter: for, the answers to this "why" and this "how" lie in the realm of things which are beyond the reach of human perception (al-ghayb).
I.e., "lest thou prove to be one of those ignorant who ask God that He change His decrees in response to their own desires" (Manar XII, 85 f.).