Work hard so you can present yourself to God and receive his approval. Be a good worker, one who does not need to be ashamed and who correctly explains the word of truth.
2 Timothy 2:15 NLT

Heaven is a free gift. But we have work to do.

The work it’s talking about is the Harvest of God. We as his children should understand His Word enough to share it with other people. Then by his grace, while we use the Living Word of God, the Holy Spirit takes over and fills the person you’re sharing with the love of God if they receive it.

http://learn.evangelismexplosion.org/xee/life-forever/video/

WORK HARD https://app.backtothebible.org/en/messages/562?orgid=399 via @Beyond Sundays