Génesis 38:9

9 Y sabiendo Onán que la simiente no había de ser suya, sucedía que cuando entraba a la mujer de su hermano corrompía en tierra, por no dar simiente a su hermano

Génesis 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:

Génesis 38:9 In-Context

7 Y Er, el primogénito de Judá, fue malo a los ojos del SEÑOR, y lo mató el SEÑOR

8 Entonces Judá dijo a Onán: Entra a la mujer de tu hermano, y haz parentesco con ella, y levanta simiente a tu hermano

9 Y sabiendo Onán que la simiente no había de ser suya, sucedía que cuando entraba a la mujer de su hermano corrompía en tierra, por no dar simiente a su hermano

10 Y desagradó en ojos del SEÑOR lo que hacía, y lo mató también a él

11 Y Judá dijo a Tamar su nuera: Estate viuda en casa de tu padre, hasta que crezca Sela mi hijo; porque dijo: Que por ventura no muera él también como sus hermanos. Y se fue Tamar, y estuvo en casa de su padre