Go back and it is saying to think about what is being given to them, Revelation from God, but they are denying it. 34:47 is just stating to THINK, either alone or with others so that you reach the right decision about this issue. Stand up means do something instead of going along with the crowd, unthinking.
34:43 When Our verses are conveyed to them in all clarity, they say, "This is only a man who wants to divert you from what your ancestors used to worship.” And they say, “This is nothing but an invented lie.” Those who disbelieve say of the truth when it reaches them, “This is nothing but an obvious magic."
34:44 But We never gave them any scriptures that they study, nor did We send to them before you any warner.
34:45 Thus too, those before them had denied. These (people) have not received a tenth of what We had granted to those. Yet, when they denied My Messengers, (see) how awesome was My rejection!
34:46 Say, "I ask you to do just one thing: For the sake of God! Stand up in pairs and singly, and then think. There is no madness in your companion. He is only a warner to you in the face of a terrible doom."
34:47 Say, "I have never asked you any reward but (all my effort) is in your interest. My reward rests with none but God, and He is Witness to everything."
34:48 Say, "Surely, my Lord makes the truth prevail - He Who is the Profound Knower of the Unseen."
34:49 Say, "The truth has now come. And falsehood can neither initiate anything, nor repeat it." [17:81. True ideas are inherently creative. falsehood, being itself an illusion, cannot really create anything]
Or more explanation:
34;43. The condition of these people is such that when Our clear Laws (message) are presented to them, they incite people by saying that this person wants to turn you away from the path which your ancestors used to follow; (and the path he wants you to follow is from God). All this is a falsity which he has fabricated and attributed to Allah. When the truth is presented to these people, they say that it is nothing but pure and open falsehood.
34;44. (Just ask them, "As you never use intellect and reason in reaching a decision rationally and only follow your ancestors blindly, how have you come to know that this message is not Wahi and is my own created lie?) Also never has any Rasool come to you and given you God’s Book which after you have read it, would let you conclude that whatever I say is not Wahi; and that the style of Wahi is different. On what basis do you say that the Quran is not revealed from Allah?”
34;45. (In actual fact these people are saying this blindly, out of sheer prejudice and ancestor following and) Like-wise previous generations also used to belie the Wahi. These earlier people were given so much sustenance that the present generation has not received even one tenth of that. Ask them, "Do you know their fate in the end?” (In spite of all their power, strength and resources they were destroyed. So how can you get away?)
34;46. Tell them (O Rasool!), "I neither want to enter into unnecessary lengthy discussions with you nor do I want to give you a long lecture. All I ask of you is, whether in pairs or alone, that you stop for a while and think only for the sake of Allah. If you set the process of thinking using your intellect and reason, you will see for yourself that this Rasool (who is counselling you day and night) is not insane. (Whatever he says is based on intellect and reason. On this basis) He is forewarning you about the destructive results of your erroneous ways.”
34;47. Tell them O Rasool," Whatever I ask of you is for your own good. (I have no personal gains to achieve in this.) I do not ask for any reward from you; as my reward rests with Allah the Almighty, whose ever watchful eye is seeing everything."