B'resheet 44:1-5 Then he commanded his house steward, saying, "Fill the men's sacks with food, as much as they can carry, and put each man's money in the mouth of his sack. And put my cup, the silver cup, in the mouth of the sack of the youngest, and his money for the grain." And he did as Yosef had told him. As soon as it was light, the men were sent away, they with their donkeys. They had just gone out of the city, and were not far off, when Yosef said to his house steward, "Up, follow the men; and when you overtake them, say to them, 'Why have you repaid evil for good? 'Is not this the one from which my lord drinks, and which he indeed uses for divination? You have done wrong in doing this.' "
He indeed uses for divination - This comment made by the steward may have been made to throw the brothers off track. Remember they still believe that Yosef is an Egyptian. Anytime G-d reveled something to Yosef it was in a dream.
Divination is strictly forbidden in the Bible.
D'varim (Deuteronomy) 18:9-12 "When you enter the land which the L-RD your G-d gives you, you shall not learn to imitate the detestable things of those nations. There shall not be found among you anyone who makes his son or his daughter pass through the fire, one who uses divination, one who practices witchcraft, or one who interprets omens, or a sorcerer, or one who casts a spell, or a medium, or a spiritist, or one who calls up the dead. For whoever does these things is detestable to the L-RD; and because of these detestable things the L-RD your G-d will drive them out before you.
B'resheet 44:6-13 So he overtook them and spoke these words to them. And they said to him, "Why does my lord speak such words as these? Far be it from your servants to do such a thing. look, the money which we found in the mouth of our sacks we have brought back to you from the land of Canaan. How then could we steal silver or gold from your lord's house? "With whomever of your servants it is found, let him die, and we also will be my lord's slaves." So he said, "Now let it also be according to your words; he with whom it is found shall be my slave, and the rest of you shall be innocent." Then they hurried, each man lowered his sack to the ground, and each man opened his sack. And he searched, beginning with the oldest and ending with the youngest, and the cup was found in Benjamin's sack. Then they tore their clothes, and when each man loaded his donkey, they returned to the city.
Let him die, and we also will be my lord's slaves - The brothers are confident that they have done nothing wrong. Little did they know that they were being framed.
B'resheet 44:14-15 When Yhudah and his brothers came to Yosef's house, he was still there, and they fell to the ground before him. And Yosef said to them, "What is this deed that you have done? Do you not know that such a man as I can indeed practice divination?"
This was an Egyptian belief. This does not mean Yosef practiced it. Yosef was still trying to disguise himself.
B'resheet 44:16-17 So Y'hudah said, "What can we say to my lord? What can we speak? And how can we justify ourselves? G-d has found out the iniquity of your servants; look, we are my lord's slaves, both we and the one in whose possession the cup has been found." But he said, "Far be it from me to do this. The man in whose possession the cup has been found, he shall be my slave; but as for you, go up in peace to your father."
How can we justify ourselves? - We cannot justify ourselves before Yeshua any more than they could justify themselves before Yosef.
Yesha'yahu (Isaiah) 53:11 ...My righteous Servant shall justify many, for He shall bear their iniquities.
We can only be justified by the one who bore our sins: Yeshua Ha Mashiach, G-d righteous servant.
G-d has found out the iniquity of your servants - They believe G-d is dealing with them because they sold Yosef into slavery years earlier.