Hebrews 6:2

the doctrine of baptisms--paired with "laying on of hands," as the latter followed on Christian baptism, and answers to the rite of confirmation in Episcopal churches. Jewish believers passed, by an easy transition, from Jewish baptismal purifications (Heb 9:10, "washings"), baptism of proselytes, and John's baptism, and legal imposition of hands, to their Christian analogues, baptism, and the subsequent laying on of hands, accompanied by the gift of the Holy Ghost (compare Heb 6:4). Greek, "baptismoi," plural, including Jewish and Christian baptisms, are to be distinguished from baptisma, singular, restricted to Christian baptism. The six particulars here specified had been, as it were, the Christian Catechism of the Old Testament; and such Jews who had begun to recognize Jesus as the Christ immediately on the new light being shed on these fundamental particulars, were accounted as having the elementary principles of the doctrine of Christ [BENGEL]. The first and most obvious elementary instruction of Jews would be the teaching them the typical significance of their own ceremonial law in its Christian fulfilment [ALFORD]. resurrection, &c.--held already by the Jews from the Old Testament: confirmed with clearer light in Christian teaching or "doctrine." eternal judgment--judgment fraught with eternal consequences either of joy or of woe.

— Jamieson-Fausset-Brown Commentary (public domain)