2 John 1:8

Look to yourselves Exactly as in Mark 13:9, excepting the emphatic pronoun; -But look yeto yourselves".

that we lose not The persons of the three verbs are much varied in our authorities. The original reading probably was, as R. V., ye lose… we have wrought… ye receive. To make the sentence run more smoothly some have made all the verbs in the first person, others have made them all in the second. For the construction comp. 1 Corinthians 16:10. The meaning is, -Take heed that these deceivers do not undo the work which Apostles and Evangelists have wrought in you, but that ye receive the full fruit of it".

a full reward Eternal life. The word -reward" has reference to -have wrought". -Apostles have done the work, and you, if you take heed, will have the reward". Eternal life is called a fullreward in contrast to real but incomplete rewards which true believers receive in this life; peace, joy, increase of grace, and the like. Comp. Mark 10:29-30.