'Master's' in the Bible

The Philistine commanders, however, were enraged with Achish and told him, “Send that man back and let him return to the place you assigned him. He must not go down with us into battle only to become our adversary during the battle. What better way could he regain his master’s favor than with the heads of our men?

Wherefore now rise up early in the morning with thy master's servants that are come with thee: and as soon as ye be up early in the morning, and have light, depart.

So David asked him, "Will you take me down to this band [of raiders]?" He said, "Swear to me by God that you will not kill me and that you will not deliver me into my master's hand! Then I will take you down to this band."