'Once' in the Bible

When once the master of the house is risen up, and hath shut to the door, and ye begin to stand without, and to knock at the door, saying, Lord, open to us; and he shall answer and say to you, I know you not whence ye are;

but I made supplication for thee, that thy faith fail not; and do thou, when once thou hast turned again, establish thy brethren.