The Leader's full message is as follows:

In the Name of God
Dear young members of jihadi volunteering groups and Mobilized Forces for Construction!
In addition to the few words stated in person during last night’s meeting[1],[ I would like to tell you]:
First: What you do is invaluable; expressing gratitude through words by people like me will never do justice [in thanking you]. May God’s gratitude be upon you, may your efforts be gratified by God.
Second: Jihadi volunteering signifies making efforts out of faith as well as maximum implementation of mankind’s capacities; and to these two there is no ending. Thus, your jihadi volunteering today can expand, improve, and increase in quality ten to a hundred-folds.
Third: The intellectual and practical improvement of volunteers—which you reported on—should not distract them and turn them away from paying basic services and handworks.  Reconstructing walls, roofs, and the house of an elderly woman in some village bless and brightens your great works.
Fourth: Publicize the slogan of “Paying service for the realization of justice and development”. Inform the millions of young people of the country on Islam’s system of wisdom, which includes hundreds of lessons, ranging from the necessity of charity, the necessity of cooperation in doing good and observing piety, the necessity of benefitting the people and the necessity of upholding justice and the like.
Fifth: The Jihad of paying service to the public benefits the volunteers even before benefitting the receivers of the service. Detaching oneself from personal interests in order to abet others brightens the heart, enhances the mind and the thought, strengthens the willpower, and above all, brings about divine satisfaction. Demonstrate this through your words and actions to those who have not stepped into the realm of voluntary service yet.
Sixth: Perfume your surroundings with the aroma of faith and good deeds by being nice and good-tempered, faithful actions, avoiding the religiously forbidden deeds, and adhering to the recommended religious deeds while doing voluntary service.
Seventh: Make sure you get the people of the region where you are volunteering involved in the task of paying service; this is itself another great service to pay to them.
Eighth: Attend to establishing connections and cooperation among jihadi volunteering groups and with organizations capable of supporting, without falling for common frustrating bureaucratic relations.
Ninth: Artistically inform the public on your works, your progress, your achievements, and your increasing capabilities. Demonstrate how beautiful and enthusiastic your successful jihad is; which relies on only a segment of human aptitudes of the country.
God’s peace and greetings be upon the purified soul of Imam Abi Ja’far al-Jawad (peace be upon him).
Friday; Dhu'l-Qa'dah 30
August 1, 2019
Sayyid Ali Khamenei

[1] Statements made during a meeting with a group of jihadi volunteering teams; August 1, 2019