Zadok is meant rather than Samuel. The High Priesthood continued in the direct descendants of Zadok as long as the monarchy lasted (see 1 Chronicles 6:8-15).
Mine anointed - in its first sense obviously means the kings of Israel and Judah Psalms 89:20; Zechariah 4:14. But doubtless the use of the term MESSIAH (Χριστὸς Christos) here and in 1 Samuel 2:10, is significant, and points to the Lord’s Christ, in whom the royal and priestly offices are united (Zechariah 6:11-15 : see the marginal references). In this connection the substitution of the priesthood after the order of Melchisedec for the Levitical may be foreshadowed under 1 Samuel 2:35 (see Hebrews 7).