I’m been giving some thought to the subject of ‘undesigned coincidences’ in the Bible. One of the pioneers of this field of exploration was J.J. Blunt, in his book Undesigned Coincidences in the Writings both of the Old and New Testaments. (published 1847; enlarged edition 1869)
Blunt presented evidence that suggested to him the possibility of a gathered people of God before the time of Moses.
Calum Miller summarises:-
Suggestion that there was an early proto-church [Blunt calls it a ‘Patriarchal church’] despite this never being mentioned:
a. Holy places: things done before the Lord (same phrase as e.g. Lev 1:3; Deut 16:16) in the same place at different times (Gen 18:22-23; 19:27; 25:22; cf. 13:18; 27:7); tent for seeking Yahweh before Tabernacle existed (Ex 33:7)
b. Priests: Melchizedek (Gen 18:14) blesses Abraham and receives a tithe; Jethro called a ‘priest of Midian’ (Ex 2:16); ‘priests’ mentioned as a class before consecration of Aaron (Ex 19:22); proto-preachers and prophets including Noah, Abraham (Gen 20:7); Balaam, Job, Enoch)
c. Priestly dress: In general, robes inseparable from priesthood (patriarchs did not sacrifice without them; also cf. Ex 28:35; 1 Sam 2:19 might be relevant); Jacob given Esau’s ‘goodly raiments’ (chamad beged) to receive blessing from Isaac before the Lord (beged always but not only used for priestly garments – alternative term salmah never used for priestly garments; chamad usually reserved for sacred objects; Greek στολη ‘stolē‘ used in LXX for Jacob’s and Aaron’s robes; Rebekah’s care and adding aroma to it indicate sacredness, cf. Ex 37:29); Joseph’s coat of many colours (Aaron’s coat was multicoloured, cf. Ex 39:1; Joseph might have been made ‘firstborn’ given Reuben’s disgracing father and Joseph’s being Rachel’s first son)
d. Rites: Jacob consecrates worship place with oil (Gen 28:18), promises to offer tithe there (28:22) and later pours drink-offering (35:1,5), cf. 31:13; imposition of hands (Gen 48); removal of shoes (Ex 3:5); bowing in worship (Gen 24:26-52; Ex 4:31; 12:27)
e. Times of worship: Sabbath kept or hinted many times before official institution (e.g. Noah sending doves at 7 day intervals; Jacob’s waiting a week after marrying Leah; Joseph’s mourning Jacob for 7 days)
f. Moral duties: All mentioned incidentally: Noah’s recognition of clean and unclean animals; Noah’s not eating the blood of an animal; denouncement of murder; adultery forbidden; oaths being binding; making of vows; fornication forbidden; marriage with uncircumcised or idolaters forbidden; a curse on seeing parents naked; purifications for entering a holy place; birthright of the eldest son; brother being commanded to marry and bear offspring from brother’s widow; priest’s daughter to be burned if a harlot; some detail of sacrifices; circumcision; sacraments.
I do not feel competent to evaluate this evidence. However, I would say that, along the the possibility of the existence of Blunt’s ‘proto-church’, the Mosaic patterns of worship need not have been completely new, but taken up pre-existing practices. The (pre-Mosaic) rite of circumcision comes to mind.