Matthew Henry's Concise Commentary
6:9,10 There are things that are never separated from salvation; things that show the person to be in a state of salvation, and which will end in eternal salvation. And the things that accompany salvation, are better things than ever any dissembler or apostate enjoyed. The works of love, done for the glory of Christ, or done to his saints for Christ's sake, from time to time, as God gives occasion, are evident marks of a man's salvation; and more sure tokens of saving grace given, than the enlightenings and tastings spoken of before. No love is to be reckoned as love, but working love; and no works are right works, which flow not from love to Christ.
Barnes' Notes on the Bible
For God is not unrighteous - God will do no wrong. He will not forget or fail to reward the endeavors of his people to promote his glory, and to do good. The meaning here is, that by their kindness in ministering to the wants of the saints, they had given full evidence of true piety. If God should forget that, it would be "unrighteous:
(1) because there was a propriety that it should be remembered; and,
(2) because it is expressly promised that it shall not fail of reward; Matthew 10:42.
Your work - Particularly in ministering to the wants of the saints.
Labour of love - Deeds of benevolence when there was no hope of recompense, or when love was the motive in doing it.