We find that Abraham and Jacob paid tithe. But nowhere it is found in Bible that God commanded man to give tithe before Sinai. So we can only conclude that there was a knowledge of tithe but an explicit commandment to give tithe was not recorded. Similarly the events related to Sabbath and commandments for keeping sabbath are not recorded but we can conclude its existence and commandment to keep it prior to Sinai through these events and verses.
Gen 2 tells us that God blessed and sanctified (set is apart for holy purpose) because in that day He rested. He rested then He blessed that day and sanctified it. What is the purpose of God blessing and sanctifying a day which is already past? It is only because God wanted that day to be observed as Sabbath by humans. When God gave the 4th commandment He gives the creation as the reason for keeping Sabbath. He tells Israelites that God blessed that day and sanctified it. So they need to keep the Sabbath Holy.
And he said unto them, This is that which the LORD hath said, To morrow is the rest of the holy sabbath unto the LORD: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning. Gen 16:23
A very very key verse in understanding the sabbath existed even before Sinai. The Old covenant was declared and ratified in Sinai but Israelites were keeping sabbath even before the covenant was ratified. It only shows that Sabbath was not a new thing which was introduced in the old covenant but something which was existing and kept but forgotten.
Another key evidence is 130 plus cultures have named the 7th day as sabbath. It again shows Sabbath is something which was existing and kept but forgotten.
Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws. Gen 16:5