The Great Commission
Jesus gave us "The Great Commission".
Then the eleven disciples went away into Galilee, into a mountain where Jesus had appointed them. And when they saw him, they worshipped him: but some doubted. And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth. Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world. Amen.
- Matthew 28:16-20 (KJV)
Other parts of the Bible reflect this.
And he said unto them, Go ye into all the world, and preach the gospel to every creature.
- Mark 16:15 (KJV)
The fruit of the righteous is a tree of life; and he that winneth souls is wise.
- Proverbs 11:30 (KJV)
We ought to work together with God on this.
For we are labourers together with God: ye are God's husbandry, ye are God's building.
- 1 Corinthians 3:9 (KJV)
But let's not get too far ahead of ourselves, because it is ultimately God who is in charge of this work.
I have planted, Apollos watered; but God gave the increase. So then neither is he that planteth any thing, neither he that watereth; but God that giveth the increase. Now he that planteth and he that watereth are one: and every man shall receive his own reward according to his own labour.
- 1 Corinthians 3:6-8 (KJV)
So why not volunteer today? There's plenty to do. 
Then saith he unto his disciples, The harvest truly is plenteous, but the labourers are few; Pray ye therefore the Lord of the harvest, that he will send forth labourers into his harvest.
- Matthew 9:37-38 (KJV)
There's no need to be ashamed of the gospel.
Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven.
- Matthew 10:32 (KJV)