Mwanzo 38:9

Lakini Onani alijua kwamba uzao haungekuwa wake, kwa hiyo kila alipokutana kimwili na mke wa ndugu yake, alimwaga chini mbegu za kiume ili asimpatie ndugu yake uzao.

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.