What The Messenger Gives You: Take It

Muslims hear this all the time: “What the messenger gives you, take it. And from what he forbids you, refrain.” But what does it mean in the context?

The fool hath said in his heart, There is no God. They are corrupt, they have done abominable works, there is none that doeth good. (Psalms 14:1)

What God bestowed upon his messenger from the people of the cities:
Belongs to God and his messenger
And to relatives
And the fatherless
And the needy
And the wayfarer[…]
That it become not a distribution between the rich among you.
And what the messenger gives you:
Take it
And from what he forbids you:
Refrain
(And be in prudent fear of God
God is severe in retribution.)
For the poor émigrés who have been turned out from their homes and their belongings
Seeking favour and approval from God
And help God and his messenger.
These are the truthful. (59:7-8)

Two questions:
• is the messenger alive or dead? He is dead.
• can this really mean “accept a huge literature never seen by or approved by the messenger which was compsed after his death”? Which is what you are meant to think

I know where I stand. I’m not telling you what to believe. I am saying that if we believe in God and the last day it behoves us to think about things for ourselves as men and not simply accept what others tell us like children.

He it is who sent down upon thee the law.
Among it are explicit proofs
They are the foundation of the law
While others are likenesses.
Then as for those in whose hearts is crookedness:
They pursue what is a likeness thereof
Seeking the means of denial
And seeking its interpretation.
And only God knows its interpretation
And those established in knowledge.
They say: We believe in it – it is all from our lord.
But only those possessed of insight take heed.
Our lord: make thou not our hearts deviate when thou hast guided us
And bestow thou upon us mercy from thyself.
Thou art the Bestower.
Our lord: thou art gathering mankind to a day about which there is no doubt.
God will not break the appointment. (3:7-9)

Original video: https://www.youtube.com/watch?v=nFFfoVTi_kw