"Where the treasure is, there the heart will be. In every effort to benefit others, we benefit ourselves. He who gives money or time for spreading the gospel enlists his own interest and prayers for the work, and for the souls to be reached through it; his affections go out to others, and he is stimulated to greater devotion to God, that he may be enabled to do them the greatest good. MB 90.1"
"For where your treasure is, there will your heart be also."
The EGW passage directly quotes and expands upon the idea presented in Matthew 6:21, that one's heart follows their treasure. The EGW passage uses this principle to explain how investing in the gospel and helping others leads to greater devotion and affection.
"And at the final day, when the wealth of earth shall perish, he who has laid up treasure in heaven will behold that which his life has gained. If we have given heed to the words of Christ, then, as we gather around the great white throne, we shall see souls who have been saved through our agency, and shall know that one has saved others, and these still others—a large company brought into the haven of rest as the result of our labors, there to lay their crowns at Jesus’ feet, and praise Him through the ceaseless ages of eternity. With what joy will the worker for Christ behold these redeemed ones, who share the glory of the Redeemer! How precious will heaven be to those who have been faithful in the work of saving souls! MB 90.2"
"For what is our hope, or joy, or crown of rejoicing? Are not even ye in the presence of our Lord Jesus Christ at his coming?"
Both passages connect faithful labor with a future reward and rejoicing in the presence of Christ. EGW expands on the idea of 'crown of rejoicing' by explicitly mentioning saved souls as a result of the believer's work.