He knowing that the children should not be his, when he went in to his brother's wife, spilled his seed upon the ground, lest children should be born in his brother's name.

But when Onan knew that the seed should not be his own, it came to pass when he went in to his brother's wife, that he spilled it on the ground, in order to give no seed to his brother.

And Onan knew that the seed would not be his: and it came to pass, when he went in to his brother's wife, that he frustrated the purpose, lest he should give seed to his brother.

and Onan knoweth that the seed is not reckoned his; and it hath come to pass, if he hath gone in unto his brother's wife, that he hath destroyed it to the earth, so as not to give seed to his brother;

But Onan, seeing that the offspring would not be his, went in to his brother's wife, but let his seed go on to the earth, so that he might not get offspring for his brother.

Onan knew that the offspring wouldn't be his; and it happened, when he went in to his brother's wife, that he spilled it on the ground, lest he should give offspring to his brother.

He, knowing that the sons to be born would not be his, when he entered to the wife of his brother, he spilled his seed on the ground, lest children should be born in his brother's name.

Et cognovit Onan, quod non sibi futurum esset semen: et erat quando ingrediebatur ad uxorem fratris sui, corrumpebat semen super terram, ne poneret semen fratri suo.

Onan knew that the seed should not be his - That is, that the child begotten of his brother's widow should be reckoned as the child of his deceased brother, and his name, though the real father of it, should not appear in the genealogical tables.

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: