Verse: I John 5:11-13
11 And the testimony [that God has given concerning His Son] is this, that God has given us eternal life, and this life is “in His Son. 12 The one who has the Son has the life; the one who does not have the Son of God does not have the life. 13 These things I have written to you who believe “in the name of the Son of God, so that you may know that you have eternal life. (NASB)

I John 5:11, and 13 both use the same preposition translated to English as:
in. Eternal life is in the Son, and those who believe in the Son have it. Nonetheless, the prepositions are different.

I John 5:11 uses the Greek word en”, a primary preposition denoting position, and instrumentality. (Strongs Exhaustive Concordance, # 1722)  Life resides “in” the position and instrumentality of the Son and Messiah. He is the instrument that brings life to us. His position of Redeemer/Savior is the cause of the gift of eternal life to us. “Eternal life is “in” the Son.”   

I John 5:13, on the other hand, uses eis”, which literally means a movement into. (Strongs, #1519)  It implies “union” to a purpose or result (indicating a point is reached or entered, of place, time, purpose, or result). Id. You who have believed in the Son, based on his position/instrumentality, you have reached his result or purpose of eternal life.

The testimony about the son “is”. It “exists” (1 John 5:11, “estin”, Strongs, #1510). Still, eternal life does not exist in time. 

[I]t is the very antithesis of time, and yet we attempt to measure it while we declare it to be immeasurable. . . .  The main idea of “eternal life” in St. John’s writings has no direct reference to time. Eternal life is possessed already by believers; it is not a thing of the future (John 3:36; John 5:24; John 6:47, 54; John 17:3). It is that life in God which includes all blessedness, and which is not broken by physical death (John 11:25). Its opposite is exclusion from God. The Pulpit Commentary, 2010 by BibleSoft, Inc. 

Prayer:   Lord, what a blessing to know we are already living in eternal life. What a blessing to know that nothing changes with death. Our eternal life has started. We thank you Yeshua (Jesus) that you came—the Anointed Messiah and we are in union now. We have reached the purpose, eternal life, and the testimony about it is real. It “exists”. Thank you. Thank you. Thank you. We can rest.