What is the exact meaning of the statement "Ein Sar Beis ha'Sohar Ro'eh es Kol Me'umah b'Yado?"
Oznayim la'Torah: It means that the governor of the jail relied on Yosef to follow-up on the work of the other prisoners who were under his charge.
Targum Yonasan: It means that, since the governor of the jail found no fault in Yosef, he did not deem it necessary to keep an eye on him 1 like he did on all the other prisoners.
Ha'Emek Davar: He put his eyes on him - presumably, his master did not put a beautiful slave like this in prison for nothing - but he did not find any fault in him.
Oznayim la'Torah: It is truly remarkable that Yosef found himself in a prison of prisoners who are all facing the death-sentence, and in spite of the fact that he was not under supervision, he made no attempt to escape - because he had trust in Hashem. Also the chief warden trusted in Yosef's virtue and trust in Hashem, that he will not flee!
Why did the chief warden trust Yosef so absolutely?
Malbim: (a) He saw that Hashem is with him, and he is virtuous and a man of faith. (b) He succeeds via Hashgachah.
Ha'Emek Davar: (a) He saw that Hashem is with him, i.e. there was no loss in his affairs. (b) He succeeds supernaturally. This shows that he is a Tzadik.