Reference for Chullin 164:44
דאמר רבי יאשיה
For it was taught: If he struck one and then struck the other,<span class="x" onmousemove="('comment',' If a woman did not wait three months after separation from her husband by divorce, immediately married again, and after seven months gave birth to a son, there is always a doubt as to the paternity of the child. It may be a nine-months' child by the first husband or a seven-months' child by the second. This child, when grown up, struck one of his mother's husbands and then struck the other. The warning at the time of striking each one is a doubtful one, for when considering each one individually there is a doubt as to whether he is his father or not; it is nevertheless regarded as a proper warning and the son would be liable to the death penalty for striking or cursing his father (cf. Ex. XXI, 15, 17) .');"><sup>20</sup></span>