See Nehemiah 2:5 on the meaning of these words. Nehemiah repeats them because he is keenly aware of his place under the king; Nehemiah is at the king’s mercy. At the same time, Nehemiah wants the king to supply his next request, that is, for letters. Acknowledging his place beneath the king makes his next request more palatable.
7 And I said to the king, “If it pleases the king, let letters be given me to the governors of the province Beyond the River, that they may let me pass through until I come to Judah,