It sounds better to say "sacred tradition" rather than "There is no scripture to back it up".
But then, that's the rub isn't it? For nowhere does the Bible tell us "Bible alone." Of course, at this point, you'll cite the Bereans and how they were so approved for testing Paul's teaching against scripture.
But I often wonder, did Paul teach them that which he taught the Corinthians when he noted that the Israelites in the time of Moses all drank the same spritual drink from the same spiritual Rock that followed them in the desert and that that Rock was Christ?
The reason why I find this interesting is because there is nothing in the Old Testament which tells us the Rock followed them in the desert. There was, however, within Jewish oral tradition at that time a belief that the Rock followed them in the desert. Hence, St. Paul is drawing on this oral tradition in teaching the Corinthians. I wonder, Stephen, would you take St. Paul to task for teaching something withoug 'scripture to back it up?'
1 Corinthians 10: RSV
[4] and all drank the same supernatural drink. For they drank from the supernatural Rock which followed them, and the Rock was Christ.
Allow me to post what I believe is an excellent note from the NAB:
(2) [4] A spiritual rock that followed them: the Torah speaks only about a rock from which water issued, but rabbinic legend amplified this into a spring that followed the Israelites throughout their migration. Paul uses this legend as a literary type: he makes the rock itself accompany the Israelites, and he gives it a spiritual sense. The rock was the Christ: in the Old Testament, Yahweh is the Rock of his people (cf Deut 32, Moses' song to Yahweh the Rock). Paul now applies this image to the Christ, the source of the living water, the true Rock that accompanied Israel, guiding their experiences in the desert.
Paul made it clear when he was teaching tradition and he also made it clear that this tradition was in the past. By that standard no "tradition" past the time of the Apostles is valid.
Please note:
1 Corinthians 11:
[2] I commend you because you remember me in everything and maintain the traditions even as I have delivered them to you.
2 Thessalonian 2:
[15] So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter.
2 Thessalonian 3:
[6] Now we command you, brethren, in the name of our Lord Jesus Christ, that you keep away from any brother who is living in idleness and not in accord with the tradition that you received from us.
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As for your eisegesis concerning the Rock, the water, and Jesus, you may have missed this.
Exodus 17:6
Behold, I will stand before you there on the rock at Horeb; and you shall strike the rock, and water shall come out of it, that the people may drink." And Moses did so, in the sight of the elders of Israel.
Numbers 20:
[6] Then Moses and Aaron went from the presence of the assembly to the door of the tent of meeting, and fell on their faces. And the glory of the LORD appeared to them,
[7] and the LORD said to Moses,
[8] "Take the rod, and assemble the congregation, you and Aaron your brother, and tell the rock before their eyes to yield its water; so you shall bring water out of the rock for them; so you shall give drink to the congregation and their cattle."
[9] And Moses took the rod from before the LORD, as he commanded him.
[10] And Moses and Aaron gathered the assembly together before the rock, and he said to them, "Hear now, you rebels; shall we bring forth water for you out of this rock?"
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[11] And Moses lifted up his hand and struck the rock with his rod twice; and water came forth abundantly, and the congregation drank, and their cattle.