Thanks for asking. The faithful slave is the body of Christ - the anointed of God, who faithfully carry out the work Jesus started on earth. They are appointed for this purpose.
Recall that when Jesus was on earth, he started a work, of which he said, “I must also declare the good news of the Kingdom of God to other cities, because for this I was sent.”
Luke 4:43;
Luke 8:1
Before leaving the earth, he said, “All authority has been given me in heaven and on the earth.
Go, therefore, and make disciples of people of all the nations, baptizing them in the name of the Father and of the Son and of the holy spirit,
teaching them to observe all the things I have commanded you. And look! I am with you all the days until the conclusion of the system of things.”
Matthew 28:18-20
"...you will receive power when the holy spirit comes upon you, and you will be witnesses of me in Jerusalem, in all Judea and Samaria, and to the most distant part of the earth."
Acts 1:8
So Christ, operating from heaven, has appointed a slave - that is, a groups of faithful followers to finish the work of preaching "this good news of the Kingdom in all the inhabited earth for a witness to all the nations,... and then the end will come".
Matthew 24:14
One slave equals a group of anointed (appointed) ones, as can be seen from scriptures such as...
Isaiah 43:10
“You are
my witnesses,” declares Jehovah, “Yes,
my servant whom I have chosen,
It is clear to me who that slave is, because they are the ones who are preaching the good news of the kingdom worldwide, in a most organized and united way, as the Lord demonstrated.
This slave is also feeding all the household, regardless of which part of the world they reside. They all get the same food, at the same time.
That would not be possible unless the source was only one, and of divine nature.
Only God can unite people of every race and nationality into one unified body, and teach them all the same truth - feeding them through one channel under his son's direction.
Isaiah 54:13;
John 6:45
This is the structure of the true organization of Jehovah.
What I find especially important, is that
- they carry, honor, and declare God's name, just like Jesus, who said, "I have made your name known to them" - John 17:6, 26
- they carry the same message Jesus preached, and commanded be preached - the Kingdom of God. Luke 8:1; Mark 1:14, 15; Acts 1:2, 3
- they utilize the same methods of Jesus, and his apostles - to every land, city, village to village, town to town, door to door, in the marketplace... etc. Luke 8:1; Acts 20:20; Acts 17:17
It's as Paul said... Romans 10:
13 For “everyone who calls on the name of Jehovah will be saved.”
14 However, how will they call on him if they have not put faith in him? How, in turn, will they put faith in him about whom they have not heard? How, in turn, will they hear without someone to preach?
15 How, in turn, will they preach unless they have been sent out? Just as it is written: “How beautiful are the feet of those who declare good news of good things!”
They try their utmost to stick to Jesus teachings, and example.
That is faithfulness, and true Christianity, is it not.