"" quotes
() Iruka's talking in between the actual Hokage's quotes

Episode 37 6:45
"If you do not possess Heaven, gain knowledge and be prepared." (That means that if Naruto's weak point is his brain, he should study and prepare for his missions)

Episode 37 7:02
"And if you do not possess Earth, run through the fields and seek Strength" (For example, if Sakura's weakness lies in strength, she should train herself everyday)

(And if you have both Heaven and Earth attributes, any dangerous mission will become safe. It can even become easy)