Midrasz do Samuela I 10:1

“Orpa kissed her mother-in-law.” All kisses are of licentiousness, except for three: A kiss of greatness, a kiss of absence, and a kiss of parting. A kiss of greatness, as it is written: “Samuel took a flask of oil, and poured it on his head, and kissed him” (I Samuel 10:1). Of absence, as it is written: “He met him at the mountain of God at Ḥorev [and he kissed him]” (Exodus 4:27). Of parting, as it is stated: “Orpa kissed her mother-in-law.” Rabbi Tanḥuma said: Even a kiss of closeness, as it is stated: “Jacob kissed Rachel” (Genesis 29:11). Why? It is because she was his relative.
“She said: Behold, your sister-in-law has returned to her people, and to her god; return after your sister-in-law” (Ruth 1:15).
“She said: Behold, your sister-in-law has returned [to her people, and to her god]…” – once she returned to her people she returned to her god.

Another interpretation (of Exod. 4:27): AND KISSED HIM. All kisses are indecent except three, and these are the following: the kiss of departure, the kiss of greatness, and the kiss of reunion (literally: of crossroads).¹¹⁷Exod.R.5:1. The kiss of departure <is not silly> because it is stated (in Ruth 1:14): AND ORPAH KISSED HER MOTHER-IN-LAW; the kiss of greatness, because it is stated (in I Sam. 10:1): THEN SAMUEL TOOK THE FLASK OF OIL, POURED IT UPON HIS HEAD, AND KISSED HIM….; the kiss of reunion, because it is stated (in Exod. 4:27): SO HE WENT TO MEET HIM <ON THE MOUNTAIN OF GOD> AND KISSED HIM.

Have kissed each other (Ps. 85:11) tells us that he kissed him. Our rabbis teach us that all but three kinds of kisses are frivolous. Those not frivolous are the kiss of parting, the kiss of homage, (and) the kiss of reunion. How do we know about the kiss of parting? From the fact that it is written: And Orpah kissed her mother-in-law Ruth (Ruth 1:14); the kiss of homage we know from what is written: Then Samuel took the vial of oil, poured it upon his head, and kissed him (I Sam. 10:1); we know about the kiss of reunion because it is written: And he went, and met him in the mountain of God and kissed him (Exod. 2:27).