NET

9 But Onan knew that the child would not be considered his. So whenever he slept with his brother’s wife, he wasted his emission on the ground so as not to give his brother a descendant.

Darby

9 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.

KJV

9 And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled [it] on the ground, lest that he should give seed to his brother.

Strong's

9 And Onan^H209 knew^H3045 that the seed^H2233 should not be his; and it came to pass, when^H518 he went in^H935 unto his brother's^H251 wife^H802, that he spilled^H7843 it on the ground^H776, lest^H1115 that he should give^H5414 seed^H2233 to his brother^H251.