"God is not unjust to forget" is not to focus on the reward for services, but God knows the real situation of people's spiritual lives and he can motivate the expressions of 'genuine Christianity' anytime, just like in the past, also again in the future. The "work" and the "love" are those done literally 'for his name', involving the ministering of God's people (Greek: tois hagiois; "to the saints"), for example in .
