Mark 9:37 “Whoever receives one such child in my name receives me, and whoever receives me, receives not me but him who sent me.”
Psalm 138:6 Though the Lord be high, yet hath he respect unto the lowly: but the proud he knoweth afar off.
"receives me"; the receiver, receives in Jesus' name. He is identified with Jesus, humble, willing to serve the least for his sake, in his name. With that attitude, he receives the least and, guess what? He receives Jesus himself, for Jesus is with those who really are the least. There are those who take the position of least to serve, and those who really are least in a society - Jesus is with them. But he's also with those who humble themselves in service, for they get to receive him, and in turn, receive God in their lives and work. God the Father is even there with that child as well.
God tends to esteem the least - those we do not regard; they are more likely to be poor in spirit and humble, which God likes. Plus, he is tender and compassionate; he sees their suffering and it bothers him and moves him; he wants to be with them, to identify with them: you receive such, pay attention to them, think about them and open your heart to them like I do, you receive me at the same time because that's where I am in human society.