'Old' in the Bible

Nicodemus saith unto him, How can a man be born when he is old? can he enter a second time into his mother's womb, and be born?

The Jews therefore said unto him, Thou art not yet fifty years old, and hast thou seen Abraham?

Verily, verily, I say unto thee, When thou wast young, thou girdedst thyself, and walkedst whither thou wouldest: but when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and carry thee whither thou wouldest not.