One can receive the Written Torah only passively.
One who receives the Oral Torah, however, proceeds to act on it, engaging in creative thinking, deep experiencing, and specific behavior.
And unlike the Written Torah, which is not given to change, erasure, or adjustment, the Oral Torah can be altered and improved and is constantly being enlarged, added to, re-created, and enhanced by ever higher levels of experience.
That is, the day is the time for receiving the light, and the night is the time for creating.
There is a time to perceive, to look out and absorb things, and there is a time to develop what has been absorbed and even to fashion new things out of this knowledge.
It is in some ways like the photographic cycle–an instant of absorbing the light and a dark-room process of development.
–Rabbi Adin Steinsaltz
From In the Beginning by Rabbi Adin Steinsaltz