"were you not sent for? is it your own inclining? is it a free invitation?"-Hamlet
for what reason would they have sent for us
i know the king and queen have sent for you
"my lord, we were sent for"-Guildenstern
"Nay, then, I have an eye of you.-if you love me, hold not off"
in this part of the scene, Hamlet is questioning the reason of why his friends that he rarely see's have suddenly come to visit him, especially at a time where he had just found out that there could be a chance that his father has been murdered
Hamlet finally comes clean and tells them that he knows that their real reason that they are visiting him is not to be with him, but because they have been sent by the king and queen to spy on him, it's just Hamlet doesn't know exactly why
in this part of the scene, Hamlet gave the two friends pressure by basically saying if they cared about him, then they would tell him the true reason why they are there and if they had truly been called by the king and queen to spy on him