Gray hair

Does not make one an elder.

Someone ripe only in years

Is called "an old fool."

It is through truth,

Dharma, harmlessness, restraint, and self-control,

That the wise one, purged of impurities

Is called "an elder." (Verse 260-261)

The Eightfold Path consists of eight practices: right view, right resolve, right speech, right conduct, right livelihood, right effort, right mindfulness

As a person who generates the spirit of enlightenment and then promises to train in the bodhisattva deeds, you have promised to endow all living beings with the ornament of the ethical discipline of the perfect buddhas; therefore, you must accomplish the aims of all beings. In this regard you must first develop the strength of your own pure ethical discipline, for, if your own ethical discipline is impure and degenerates, you will fall to a miserable rebirth and will therefore not even achieve your own welfare, never mind the welfare of others. Hence, once you begin working for the welfare of others, value highly your ethical discipline. You need to sharply focus on safeguarding it and restraining your behavior. Do not be lax.

Thanissaro Bhikkhu. The Dignity of Restraint.