“See that you do not despise one of these little ones, for I say to you that their angels in heaven continually see the face of My Father who is in heaven. [For the Son of Man has come to save that which was lost.] What do you think? If any man has a hundred sheep, and one of them has gone astray, does he not leave the ninety-nine on the mountains and go and search for the one that is straying? If it turns out that he finds it, truly I say to you, he rejoices over it more than over the ninety-nine which have not gone astray. So it is not the will of your Father who is in heaven that one of these little ones perish.”
v.6 “...but whoever causes one of these little ones who
believe in Me to stumble...”
v.10 “See that you do not despise one of these little ones,
for I say to you that their angels in heaven continually see
the face of My Father who is in heaven.”
v.14: “So it is not the will of your Father who is in heaven
that one of these little ones perish.”
In this context, Jesus is specifically talking about His own
children (i.e. “who believe in Me”, who stumble, who go
astray, whom God comes to rescue and the angels celebrate,
per the parallel passage of Luke 15:4-7.) This is silent on
non-Christians. For a more general perspective, I suggest
Matthew 9:36.
To a Calvinist, this only refers to Calvinism’s elect “little ones.” In fact, any verse that speaks of God’s love and desire to save anyone, will be interpreted by Calvinists as referring to a special class.
John Calvin: “For the whole point of Christ’s words is that we are to take care not to lose what God wishes to save. Luke’s account has a rather different object: because the whole human race belongs to God, those who are estranged are to be gathered in, and it is as much cause for rejoicing when the lost reform as when someone finds something precious which he had given us for lost.” (Calvin’s New Testament Commentaries, A Harmony of the Gospels: Matthew, Mark and Luke, Vol. II, p.219, emphasis mine)
Now wait, if you are a Calvinist who believes in the “Sovereignty of God,” Unconditional Election, Irresistible Grace and Determinism, how could you possibly “lose what God wishes to save”? Calvinists believe that in order for God to be sovereign, everyone whom He wishes to be saved, must be saved and will be saved. However, here you have an example of Calvin overturning that whole line of thought, when he warns us not to “lose what God wishes to save.”