In short
These little ones
(Matthew 10:42) are the apostles, who are seen as simple and weak by the world, but when others honour them as God’s emissaries, those who do so will be rewarded—a promise underlined by Jesus words truly, I say to you.
The text identifies the apostles as these little ones,
which serves to indicate that they are simple people who have been disdained and persecuted as they travel through the world to preach the gospel. Nonetheless, as disciples of Jesus they are God’s emissaries. This is why those who offer a disciple of Jesus some small assistance, will necessarily receive their reward. Jesus here promises this solemnly—he guarantees it with the words truly, I say to you.
1
42 And whoever gives one of these little ones even a cup of cold water because he is a disciple, truly, I say to you, he will by no means lose his reward.”