Genesis 38:9

9 Da aber Onan wußte, daß der Same nicht sein eigen sein sollte, so geschah es, wenn er zu dem Weibe seines Bruders einging, daß er ihn verderbte zur Erde, um seinem Bruder keinen Samen zu geben.

Genesis 38:9 Meaning and Commentary

Genesis 38:9

And Onan knew that the seed should not be his
Should not be called a son of his, but a son of his brother Er; this is to be understood only of the firstborn; all the rest of the children born afterwards were reckoned the children of the real parent of them; this shows this was a custom in use in those times, and well known, and was not a peculiar case: and it came to pass, when he went in unto his brother's wife;
to cohabit with her, as man and wife, he having married her according to his father's direction: that he spilled [it] on the ground, lest he should give his seed to
his brother:
lest his brother's wife he had married should conceive by him, and bear a son that should be called his brother's, and inherit his estate; and this is the sin, which from him is called Onania, a sin condemned by the light of nature, as well as by the word of God, and very prejudicial to mankind, as well as displeasing to God, as follows:

Genesis 38:9 In-Context

7 Und Gher, der Erstgeborene Judas, war böse in den Augen Jehovas, und Jehova tötete ihn.

8 Da sprach Juda zu Onan: Gehe ein zu dem Weibe deines Bruders, und leiste ihr die Schwagerpflicht und erwecke deinem Bruder Samen.

9 Da aber Onan wußte, daß der Same nicht sein eigen sein sollte, so geschah es, wenn er zu dem Weibe seines Bruders einging, daß er ihn verderbte zur Erde, um seinem Bruder keinen Samen zu geben.

10 Und es war übel in den Augen Jehovas, was er tat; und er tötete auch ihn.

11 Da sprach Juda zu Tamar, seiner Schwiegertochter: Bleibe Witwe im Hause deines Vaters, bis mein Sohn Schela groß sein wird. Denn er sagte: Daß nicht auch er sterbe wie seine Brüder! Und Tamar ging hin und blieb im Hause ihres Vaters.