We do not need to go far into the OT before finding Scriptural support for small groups. We see that it is not good for us to be alone.
The Lord God said, “It is not good for the man to be alone. I will make a helper suitable for him.”
Then the Lord God made a woman from the rib he had taken out of the man, and he brought her to the man. The man said, “This is now bone of my bones and flesh of my flesh; she shall be called ‘woman’ for she was taken out of man.”
The man and his wife were both naked, and they felt no shame.
Then the eyes of both of them were opened and they realized they were naked; so they sewed fig leaves together and made coverings for themselves.… And they hid from the Lord God among the trees of the garden. (Gen 2:18, 22, 25 ESV)
This simple yet powerful passage tells us a great deal about what God wants for us and our own misguided desire for independence and even equality with God. What we fail to understand far too often is that only God can bring us into community with one another and with Him.
From the Gospels we find a number of foundational passages in support of small group ministry. Jesus himself at the beginning of His public ministry assembled a small group.
Passing alongside the Sea of Galilee, he saw Simon and Andrew the brother of Simon casting a net into the sea, for they were fishermen. And Jesus said to them, “Follow me, and I will make you become fishers of men.” And immediately they left their nets and followed him. And going on a little farther, he saw James the son of Zebedee and John his brother, who were in their boat mending the nets. And immediately he called them, and they left their father Zebedee in the boat with the hired servants and followed him.(Mark 1: 16-20 ESV)
Jesus worked in groups of two or more even though when we think of a groups the 12 Disciples most often come to mind.
Finally, the elsewhere in the NT, we find several passages in Acts in support of small group ministry.
Now the full number of those who believed were of one heart and soul, and no one said that any of the things that belonged to him was his own, but they had everything in common. And with great power the apostles were giving their testimony to the resurrection of the Lord Jesus, and great grace was upon them all. There was not a needy person among them, for as many as were owners of lands or houses sold them and brought the proceeds of what was sold and laid it at the apostles’ feet, and it was distributed to each as any had need. (Acts 4:32–35 ESV).
Small groups are of one heart and look after each other in their shared physical needs as well as their spiritual needs. Helping each other and holding each other accountable are hallmarks of a strong small group.