It is tradition. Here is scripture discussing tradition.
Paul illustrated what tradition is: “For I delivered to you as of first importance what I also received, that Christ died for our sins in accordance with the scriptures. . . . Whether then it was I or they, so we preach and so you believed” (1 Cor. 15:3,11). The apostle praised those who followed Tradition: “I commend you because you remember me in everything and maintain the traditions even as I have delivered them to you” (1 Cor. 11:2).