For many years I pastored a small rural congregation in a tiny town. I used to wonder if I was a failure as a pastor because despite much effort and evangelism, my congregation had grown no bigger than 40 people. In comparison to the town population of 2500, it was in reality a successful congregation both numerically and as a percentage of the town.
In reading the gospels one day, I felt much better knowing that even the quality teaching, and quality attention of Jesus had not produced a large group of people, and the small group it had produced were not unified in purpose and didn't seem to like each other.
What the disciples had received was 3 years of quality teaching, and they each loved Christ and had a desire to serve Him, however they lacked love and value for each other that came from the heart.
Two significant things then happened. The resurrection of Christ gave them a sense of wonder and fresh focus. Then the Day of Pentecost gave them power. However this power was not just for speaking in tongues, it was power to love one another. It was community anointing. It was the spirit of understanding which changes hearts.
Now the teaching of Christ had an effect in their lives and they had grace to change. Now they found that they loved each other, they valued each other from the heart, they prayed sincerely, they even died for each other. The church grew rapidly… things were different to before.. And during all of this, Jesus wasn't even physically present.
From before to after was as different as chalk and cheese. It is an example of what happens when a people receive the spirit of understanding.