This might be true; but where is it recorded?
Did GOD tell Juda to tell him?
Juda, therefore said to Onan his son...
IF I live by sticking to the Scriptures...
It appears that Onan died because he dishonored his father's command.
This might be true; but where is it recorded? Did GOD tell Juda to tell him? Juda, therefore said to Onan his son... IF I live by sticking to the Scriptures.
Sticking to the Scriptures means going by what it teaches, which as in everyday life means what is communicated in the many genres and means employed,and via precept as well as the principal behind them, the use of which Scripture itself affirms and examples. In contrast, restricting teaching to only explicit statements such as you require here (sounding like a RC in opposing SS, though Westminster even affirms the light of nature and the magisterial office) is not Scriptural or reasonable, though the more explicit and unequivocal a statement is then the stronger it the case is for the validity of its understanding.
How do we know that "Adam knew his wife" means sexually so since it is not explicitly stated? Or how do we know from the OT that Cain slew his brother due to envy since it is not explicitly stated but only implied? That he did so because his own works were evil, and his brother's righteous (1Jn. 3:12) is affirmed under the NT, thus further indicating it was due to envy.
Here, how do we know here that the sin of Onan was quite evident to be selfish disobedience to God? Because first the text plainly states that "Onan knew that the seed should not be his...that he spilled it on the ground, lest that he should give seed to his brother," (Genesis 38:9) thus if the seed would have been his then he would not have prevented conception, which was rather obviously due to selfishness. That it was disobedience to God is what may be contended, but in the light of the later law mandating this (Dt. 25:5-10; cf. Ruth 4:10) it infers that at least they were doing "by nature" what is in the Law, (Rm. 2:14) which has God as its author.