You have completely twisted Jacob’s prayer out of context to suit your own desires.
1. Jacob the supplanter (not Israel) was telling God what to do – not a good example for Christians to follow. Notice the “if” condition.
2. Jacob commanded God to protect him and bless him first, and then he would return a tithe.
3. According to Deuteronomy 28 to 30 and Galatians 3:10, the whole law was a test – obey ALL to be blessed; break ONE to be cursed. It is foolish to think that God would bless a Hebrew for tithing while he was breaking many of the other 600 plus commands of the whole law.
4. Jacob did not believe his own vow. While returning and fearing Esau, he was willing to sacrifice his lesser wives and lesser children by placing them at the forefront to be slaughtered.
5. Jacob’s tithe was from defiled pagan dust. It was not a HOLY tithe of food from inside God’s HOLY land as required by the Law and as applied in Malachi 3:10 and Matthew 23:23. Again, this was not an example for Christians.
6. God never placed Gentiles or the Church under the Law and He never commanded them to tithe. New Covenant giving is freewill and sacrificial. Please stop abusing God’s Word to teach error.