John 17:3 - Eternal Life is a Supreme Relationship with Jesus Christ.

John 17:3 (KJV)  And this is life eternal, that they might know thee the
only true God, and Jesus Christ, whom thou hast sent.

John 17:3 (TLB)  And this is the way to have eternal life--by knowing you,
the only true God, and Jesus Christ, the one you sent to earth!

This is Christ's definition of salvation, [Ryrie SB]

Christ defined eternal life as intimate personal knowledge of Father and
Son. Eternal life is not a possession but an eternal relationship. [Disciple
SB]

Jesus gives eternal life to all who receive Him. This eternal life consists
in fellowship with God through saving faith in Jesus Christ. [Passages Of
Life SB]

How do we get eternal life? Jesus tells us clearly here - by knowing God the
Father himself through his Son, Jesus Christ. Eternal life requires entering
into a personal relationship with God in Jesus Christ. [Life Application SB]

The way to attain this eternal life is to acknowledge, worship, and obey,
the one only true God, and to accept as teacher, sacrifice, and Saviour, the
Lord Jesus, the one and only true Messiah. (Adam Clarke Commentary)

Experimental, living knowledge leads to life eternal. There is no salvation
in knowledge alone, but neither can there be salvation without knowledge.
[SDA Commentary]

The experimental knowledge of God and of Jesus Christ whom He has sent,
transforms man into the image of God. It gives to man the mastery of
himself, bringing every impulse and passion of the lower nature under the
control of the higher powers of the mind. It makes its possessor a son of
God and an heir of heaven. It brings him into communion with the mind of the
Infinite, and opens to him the rich treasures of the universe.  COL114

Jesus defined eternal life. To experientially, progressively know . . . God,
and his Son, Jesus Christ, is eternal life. In other words, eternal life is
the ongoing knowledge of the Father and the Son. [Jamieson, Fausset, And
Brown Commentary]

Eternal life, as defined here by Jesus, involves the experience of knowing
the only true God through His Son (cf. Matt. 11:27). It is a personal
relationship of intimacy which is continuous and dynamic. The word know
(gino4sko4sin) here in the present tense, is often used in the Septuagint
and sometimes in the Greek New Testament to describe the intimacy of a
sexual relationship (e.g., Gen 4:1, "lay"; Matt. 1:25, "had... union"). Thus a
person who knows God has an intimate personal relationship with Him. And
that relationship is eternal, not temporal. [Bible Knowledge Commentary]

The Old Testament regularly uses know for sexual knowledge. "Adam knew Eve
his wife, and she conceived, and bore Cain" (Gen 4:1). Now the knowledge of
husband and wife is the most intimate there can be. Husband and wife are no
longer two; they are one flesh. The sexual act itself is not the important
thing; the important thing is the intimacy of heart and mind and soul which
in true love precede that act. To know God is therefore not merely to have
intellectual knowledge of him; it is to have an intimate
personalrelationship with him, which is like the nearest and dearest
relationship in life. [Barclay Commentary]

Those that are brought into union with Christ, and live a life of communion
with God in Christ, know, in some measure, by experience, what eternal life
is,... The knowledge of God and Christ leads to life eternal; this is the way
in which Christ gives eternal life, by the knowledge of him that has called
us <2 Peter 1:3>, and this is the way in which we come to receive it....
To know him as our Creator, and to love him, obey him, submit to him, and
trust in him, as our owner ruler, and benefactor,-- to devote ourselves to
him as our sovereign Lord, depend upon him as our chief good, and direct all
to his praise as our highest end,-- this is life eternal. (Matthew Henry's
Commentary)

This is the source of eternal life; or it is in this manner that it is to be
obtained. The knowledge of God and of his Son Jesus Christ is itself a
source of unspeakable and eternal joy.... The word "know" here, as in other
places, expresses more than a mere speculative acquaintance with the
character and perfections of God. "It includes all the impressions on the
mind and life which a just view of God and of the Saviour is fitted to
produce." It includes, of course, love, reverence, obedience, honor,
gratitude, supreme affection. "To know God as he is" is to know and regard
him as a lawgiver, a sovereign, a parent, a friend. It is to yield the whole
soul to him, and strive to obey his law.... Simply to have heard that there is
a Saviour is not to know it. To have been taught in childhood and trained up
in the belief of it is not to know it. To know him is to have a just,
practical view of him in all his perfections as God and man; as a mediator;
as a prophet, a priest, and a king. It is to feel our need of such a
Saviour, to see that we are sinners, and to yield the whole soul to him,
knowing that he is a Saviour suited to our needs, and that in his hands our
souls are safe. In this verse is contained the sum and essence of the
Christian religion, as it is distinguished from all the schemes of idolatry
and philosophy, and all the false plans on which men have sought to obtain
eternal life. (Barnes' Notes)

Merrill Tenney suggests that "life is active involvement with environment;
death is the cessation of involvement with the environment." A worm has an
earthly life, in that its environment is the dirt in which it lives. It has
no capacity to interact with an environment of water or air.Similarly human
beings have biological life that enables them to interact with the
biosphere: the realm of life on earth. But human beings have no native
capacity to interact with the realm of the spiritual and eternal. Unless
they have come to know God through Jesus Christ, and have been given eternal
life by God.What an insight into the nature of our "eternal life." It is not
simply endless. It is the capacity now to be involved with God: to speak to
Him, to be guided by Him, to be empowered by the Holy Spirit. We live with
our feet on the ground. But our native environment now is eternity, and our
primary relationship is with God. [The 365-Day Devotional Commentary]

We can know some things about God by observing His creation; but in order to
know God, Himself, this verse says that Jesus Christ must reveal Him to us.
If you are a born again believer, it is because Jesus Christ revealed
Himself to you:  He opened your spiritual eyes to see; He unplugged your
spiritual ears to hear; He softened your heart to respond.  Because we are
chosen, we should respond by searching out for ourselves all that is
involved in being a child of the Living God.  There is so much we do not yet
understand about our new life; there is even more that we do not understand
about our new Father.  Begin today by determining to know Jesus Christ
better each day. [In His Time; Walk With Wisdom re Luk.10:22]

No man, without divine aid, can attain to this knowledge of God. The apostle
says that "the world by wisdom knew not God." 5T737-41

In Psa.46:10 the Lord calls us to silence and inactivity if we want to know
Him intimately. If it were not necessary, He would not admonish us to do it.
The language is so simple and direct and yet we continue to rattle off
non-stop chatter as we rush along the fast-track going our own way!  Why do
we do that? It takes self discipline and the help of the Holy Spirit to be
silent.  Even if we close our mouths, our minds race from one thing to
another:  the unexpected meetings; the unending errands; the unwritten
letters; and the unreturned phone calls. When is the last time you set aside
everything else to be still before God?  If you sincerely want to know Him
intimately, you will schedule some time soon!  How about today?  [In His
Time; Walk With Wisdom]

They walked in the sparks (their bright flashes of thought) of their own
kindling. They did not depend on the wisdom which God alone can give. MYP186

He never insists on obedience, but when we truly see Him we will instantly
obey Him. Then He is easily Lord of our life, and we live in adoration of
Him from morning till night. [In His Time; My Utmost For His Highest re
Joh.13:13]

Men who are not saved by the grace of Christ do not live, they only exist,
(Adam Clarke Commentary)

One Sunday a plainly dressed, scholarly-looking man went into a church in
the Netherlands and took a seat near the pulpit. A few minutes later, a
woman approached the pew. Seeing the stranger, she curtly advised him that
he was in "her seat" and asked him to leave. The man apologized and moved to
one of the pews reserved for the poor. There, he devoutly joined in the
service and left afterward without further incident.When the service was
over, one of the woman's friends asked her if she knew who it was whom she
had ordered out of her pew. "No," the woman replied casually, "only some
stranger, I suppose."To the woman's great dismay, her friend informed her
"It was King Oscar of Sweden. He is here visiting the Queen."People who
refuse to acknowledge the existence of God simply aren't aware of Who is
walking beside them day by day. We can refuse to recognize God, but that
does not mean He ceases to exist or that He stops reaching out to us with
His great love. Although the Lord may be invisible to us now, He is more
real than anything we can see with our natural eyes. Rest in the knowledge
that God is with you today, tomorrow and forever. [God's Little Devotional
Bible]

One may think of God as the "Force" or some other abstract idea.  And as
long as an individual thinks this, there shall be no growth in knowing God.
[In His Time; Walk With Wisdom]