O Lord, I beseech thee, let now thine ear be attentive to the prayer of thy servant, and to the prayer of thy servants, who desire to fear thy name: and prosper, I pray thee, thy servant this day, and grant him mercy in the sight of this man. For I was the king's cupbearer. Mercy in the sight of this man - Favour before the king, Ahasuerus. He seems then to have been giving him the cup.
For I was the king's cup-bearer - The king's butler, (the Persians call him saky), which gave him the opportunity of being frequently with the king; and to be in such a place of trust, he must be in the king's confidence. No Eastern potentate would have a cup-bearer with whom he could not trust his life, poison being frequently administered in this way. This verse seems to have been a mental prayer, which Nehemiah now put up as he was delivering the cup into the king's hand.
Commentary on the Bible, by Adam Clarke [1831].