Psalms of Solomon 17:40
38 And the blessing of the Lord will be with him in strength, and it will not weaken. 39 His hope will be in the Lord. Then who can be stronger than he? 40 He will be mighty in his actions and strong in the fear of God, faithfully and righteously shepherding the Lord's sheep, he will not let any of them stumble in their pasture. 41 He will lead them all impartially, and there will be no arrogance among them that any of them should be oppressed. 42 This is the magnificence of the king of Israel that God acknowledged, to raise him over the House of Israel to discipline it.
Matthew 18:12
10 “See that you do not disdain one of these little ones. For I tell you that their angels in heaven always see the face of my Father in heaven. 12 What do you think? If someone owns a hundred sheep and one of them goes astray, will he not leave the ninety-nine on the mountains and go look for the one that went astray? 13 And if he finds it, I tell you the truth, he will rejoice more over it than over the ninety-nine that did not go astray. 14 In the same way, your Father in heaven is not willing that one of these little ones be lost. 15 “If your brother sins, go and show him his fault when the two of you are alone. If he listens to you, you have regained your brother.
Notes and References
"... Psalms of Solomon 17, which is considered the most detailed description of a pre-Christian Messianic expectation, represents the most extensive use of the Messianic Shepherd-King motif in post-biblical Judaism ... At the appearance of the Messiah, these would form the nucleus of a restored national state. Yet, in the eschaton, when Messiah’s kingdom extents to include all the nations, the Lord’s flock will expand to include the one nation Israel as well as reverent Gentiles nations. With such a significant use of the Messianic Shepherd-King motif, in a setting not so distant either temporally or socio-politically from the Gospel of Matthew, Psalms of Solomon 17 provides an important comparison to the Evangelist’s use of the motif ..."
Willitts, Joel Matthew’s Messianic Shepherd-King: In Search of "the Lost Sheep of the House of Israel" (pp. 79-90) De Gruyter, 2007