John 15:9

Exegesis for funeral of C. Wellmann, September 11th 2010.
Hymns: 256, 411 and 452 "Let Us Ever Walk with Jesus"

9 καθὼς ἠγάπησέν με ὁ πατήρ, κἀγὼ ὑμᾶς ἠγάπησα∙ μείνατε ἐν τῇ ἀγάπῃ τῇ ἐμῇ.

9 As the Father has loved me, so have I loved you. Now remain in my love.

καθὼς As, in the same way as.

ἠγάπησέν με ὁ πατήρ, The Father loved me. The aorist doesn't express a time of any kind, but just a fact as if already in the past in the mind of the speaker. The Father here is God the Father, and the article could even be one of possession "my Father" although we don't normally do that when Jesus refers to his own Father.

κἀγὼ I also, κἀγὼ is a conjunctive pronoun; more than a third of the 76 occurrences of this word are in John's Gospel.

ὑμᾶς ἠγάπησα, loved you, ἠγάπησα∙ is another aorist (ἀγαπάω), again expressing a fact rather than a certain moment in time.

μείνατε ἐν τῇ ἀγάπῃ τῇ ἐμῇ. remain in my love. μείνατε "remain" aorist imperative 2nd plural from μένω, "stay, remain." ἐν τῇ ἀγάπῃ "in...love" states the dative of sphere in which this remaining is to take place. τῇ ἐμῇ is a dative of possession.

Luther: 

As has been said before, the reason for this command is that Christ foresaw how the devil would sow discord, anger, impatience, hatred, and envy in Christendom. Unfortunately we, too, have seen all too much of this all along, and it is still in evidence. We are branches that must constantly be pruned and purged. Even though we are clean in Christ if we remain in Him, still we are not yet completely clean in our lives; for we are encumbered with this mortal frame and with many daily frailties and shortcomings. It is inevitable that one member occasionally jostles the other, just as a foot or a toe of our body bumps the others, or as a person injures himself. Such bumps and trials do not fail to come, especially because we are sojourning here in the realm of the devil, who tempts us uninterruptedly, and also because the flesh is still weak and full of flaws. This explains why even dear and faithful friends fall out or become irritable with one another. At times the devil injects poison and suspicion into a heart because of a single word or glance and thereby stirs up mutual animosity. He is a master in this art and devotes himself to it most diligently. He employs his craftiness before one is really aware of it. (LW 24)

Because of the troubles we have in life, Jesus urges us (the aorist imperative is a very strong command: You must remain in me!) to keep ourselves with him, in fact within him at all times. This is best explained with the meaning of the Greek dative case and the preposition "in" (ἐν). This construction presents a sphere in which the believer exists, within the love and grace of Christ himself. We remain (μένω) in his sphere by faithful attention to the gospel in word and sacrament.