COMMENTARY on 12:50
A. Yusuf Ali:

Translation:
So the king said: "Bring you him unto me." 1707 But when the messenger came to him, (Joseph) said: "Go you back to your lord, and ask him, ´What is the state of mind of the ladies who cut their hands´? 1708 For my Lord is certainly well aware of their snare." 1709
Commentary:

1707  The cupbearer must have reported Joseph's interpretation to the king, and the king naturally wanted to see Joseph himself. He sent a messenger to fetch him.

1708  The king's messenger must have expected that a prisoner would be only too overjoyed at the summons of the king. But Joseph, sure of himself, wanted some assurance that he would be safe from the sort of nagging and persecution to which he had been subjected by the ladies. We saw in verse 33 above that he preferred prison to their solicitations. He must therefore know what was in the mind of the women now.

1709  If the king ("thy lord") did not know of all the snares which had been laid for Joseph by the ladies, Allah ("my Lord") knew all their secret motives and plots.