Compassion demands that we help those who we see to be struggling under a burden. We would do this even with an animal; how much more with a fellow believer.
What we should focus on is that we fulfil the law of Christ, we please our Lord and Saviour who loves kindness when we come alongside those who are struggling with the burdens of life and offer to help carry those burdens with them. Never mind that our strength is also limited. The offer of help is what is so comforting to a burdened soul. It tells them that they are not alone and it tells them that Christ has brought help into their lives. Though our help is limited, his help is unlimited, and our help is a token to them that he will not fail them. Christ could of course lift their burden altogether, but by allowing them to feel the weight of it and by allowing another weak and fallible creature to come to their aid, he creates a situation in which our limited help is a genuine expression of love according to our ability. Christ thereby fosters kindness and love throughout his kingdom so that it becomes known as an oasis in a dry and thirsty land.
How does that law of Christ differ from the Mosaic law? Christians may not be under the Mosaic law but they are not without law altogether: they are under the law of Christ. The same term is used in 1 Corinthians 9:21. The law of Christ is not different in form to the law as it is in the Old Testament: the difference is that the believer is in a totally different relationship to that law. Having been set free from it as a means of obtaining life, he may now return to it as a revelation of the will of Christ for his life, as that which expresses the Lord’s will for his people. Christ summarized the law in the new commandment which he gave to his disciples (John 13:34) and which John also tells us is an old commandment (1 John 2:7). We may more realistically fulfil this law than we could ever fulfil the law of Moses for he have a new motive for obeying God and we have God’s own example to follow, and we have the Spirit of God writing his commandments on our hearts.