The Apostle Paul in his letter to the Romans writes about the doctrine of Justification and the Law of Moses. In his letter he introduces the reader to the law of the grace, the law of the spirit, clarifying that everyone will be retributed for his works, affirming: To those who by persistence in doing good seek glory, honor and immortality, he will give eternal life. Romans 2:7
In this teaching appear two interrelated concepts between them: Immortality and eternal life.
Jesus explains eternal life to us: "This is eternal life, that they may know you the only true God," John 17: 3. Thomas Aquinas in his book Summa Theologiae explains: eternal life is contemplative activity. These teachings of eternal life are very brief. We can extend this teaching in another way.
Eternal Life is a set of blessings that God gives as an advance in life in glory and between this gifts is contemplative activity, the guide of God, happiness of the heart and Immortality. Eternal life is like an order of payment, like a fruit of the spirit.
The spiritual gift of Immortality appears in the Old Testament: "In the familiarity with the wisdom is the immortality", Book of Wisdom 8:17. God is immortal. God can transmit his immortality in a limited manner on the physical plane. Immortality means no mortality, it is the gift of health, longevity. When we live in the state of grace or of communion with God, the love for the good, the positive emotions emanating from this state produce an internal state of wellness which results in a long term life.
Recall that the Tao for example has a similar concept; in ancient times when life expectancy was very low, around 15-30 years to reach this precious gift was like winning the lottery, this gift was considered a mystery, a kind of holy grail of spirituality. It was common at that time that many kings and emperors seek spiritual teachers, great meditators, to achieve this Gift.
Longevity is intimately related to the contemplative activity (contemplation is the meditation focused in the divine attributes of God) and in particular with the constancy in the practice of the good and the glory. Through constancy or Serenity in good works we reach the Glory, the perfect fame, the fame of God and not only that but also the state of grace to know God as taught by Jesus Christ and receive this important gift . Good and constancy are the way for this important gift.