Jesus spent the majority of his adult life surrounded by just 12 men, yet saved the world from sin. Gideon only had 300 men yet managed to defeat the Mideonites. David beat Goliath.

One might suggest our God is a God of the underdog.

It is easy to assume that the churches that have all the money and all the people do all the good, and there is no denying that mega-churches do do good things. However, stats released by charity Christians Against Poverty show that 6/10 of the churches they worked with had a membership of 100 or less, while just 1 per cent had congregations 500 strong or more.

Chief Executive Matt Barlow said: "We have partner churches who run job clubs, debt centres, help the homeless and run a foodbank with a regular congregation of 70 worshippers. Like David and Goliath, small really can be mighty when you are working with God."

CAP's findings support what I've been thinking for a while, maybe – when it comes to churches and social action – small really is beautiful.

The word church in the Bible comes from the Greek ekklesia, which means a called out company or assembly. Wherever it is used in the Bible it refers to people.

As Frank Viola describes in From Eternity to Here,

"The word meant a local community of people who assemble together regularly. The word was used for the Greek assembly whereby those in community were "called forth" from their homes to meet in the town forum to make decisions for their city. Consequently, the word also carries the flavour of every-member participation in decision-making... It's a community of people who gather together and who possess a shared life in Christ."

The Church described in Acts 4 is a body of people so close that "no one claimed any of their possessions was their own, but they shared everything." They testified the resurrection of Jesus and God poured out his grace "that there were no needy persons among them." God calls us to live in community (church) in which self-giving love is the foundation, the natural overflow being that no one is in need. This demands sacrifice – the wealthy sold their possessions in order that the poor were not needy – but this sacrifice is worth it when the fellowship is genuine.

Founders of House2House, a ministry seeking to transform communities through house churches, Tony and Felicity Dale wrote in their book The Rabbit and the Elephant about their realisation that church was meant to be done, not attended:

"We realized that we needed to view the New Testament through the lens of a small group setting in order for it to make sense. How can you bear one another's burdens (Galatians 6:2) or teach and admonish one another (Colossians 3:16) in a congregation of 500 when you may not even know the person sitting next to you?"

It all comes down to relationship. The power of the small church is that relationships go deep and are real. This may look and feel a little messier, but real relationships in which people are known to one another fosters a sense of belonging and ownership that empowers members to engage with one another and the wider community. Church becomes more than just a Sunday club, it becomes family.

In his book What Really Matters in Ministry, theologian and pastor Darius Salter did a study of 100 churches ranging from small to mega-churches. He observed that those who were part of a large congregation often felt anonymous and unaccountable, whereas those in churches of 100 people or less felt more comforted by God's word and more challenged by his people.

You can also see how, as a smaller church, it might be easier to mobilise and organise people to act. Larger churches may have members communting in from a wide area, whereas a smaller church is more likely to have a congregation based locally. When it comes to community outreach and social action, it is easier to engage a close-knit local church as they naturally have a greater investment in the area impacted. If you are living on the estate you are serving, both the desire to serve and the service will come more naturally.

As churches grow, the number of rows of chairs (or pews) has to increase, and someone unavoidably ends up at the back. The beauty of a small church is that it is far easier to empower each member and avoid hierarchical structures which leave people feeling they are not qualified to serve. It can develop and invest in each member of the family, growing leaders of all capacities.The prominent church consultant, Lyle Schaller, said "in large congregations the emphasis is placed upon organizational leadership", whereas smaller congregations enable an "informal decision making process" where an individual member's voice is going to carry further.

As groups grow in size there is a tendency towards competition rather than collaboration, leaving some engaging in service and the others resigning to sitting in the "audience". In a smaller church each member is needed – active engagement is required – or else the show will not go on. It is easier to galvanise people to action when they know that their voice is both needed and will be heard.

Some might suggest the reason CAP's figures show that smaller churches are more likely to be doing their courses is because larger ones are running their own, and they might be right. But there is a certain sadness in this. We are called to work together humbly, not independently labelled to promote our own brand. Smaller churches are often happier to collaborate as they know they cannot do it on their own; a helpful reminder of the reality that we are not to lean on our own understanding or try and do things in our own strength, but that the truth is we are dependent on God through whom all things are possible. Larger churches are a little more at risk of relying on their own strength.

Of course, people within big churches seek to engage with social action, and many are doing just that. This is not a criticism of individuals or even big churches, rather an endorsement of the beauty of small churches, where the word "church" refers to people not a building, to the body of Christ, a community with many members working together both dependent upon and serving God, who "by their fruit you will recognize them".