Well gee, bybee, by that rationale a condom could be seen as a murder weapon.
A condom is not murder, but it can be a sin according to Bible teaching.
FIRST:
(according to the original description of a marriage)
A person not wanting children should not join in a marriage with another partner who does want to have children ... for the marriage covenant insinuates an obligation for the partners to reproduce.
Genesis 2:23, 24 KJV
And Adam said, "This
(visible manifested female wife) is now
(brought forth as) bone of my bones, and flesh of my flesh: she shall be called Wo-man because she was taken out of Man.
Therefore
(from this point onward) shall a man leave his father
(which is one who has reproduced a new one) and his mother
(a female woman who has produced offspring) and shall cleave unto his wife
(one expected to reproduce): and
they shall (also) be ONE FLESH.
The
"be ONE FLESH" ... which they become is
"a NEW FLESH" that is formed of by their separate genetic codes joining together to make
"a NEW ONE" after their likeness. IOW, a
"BABY". They literally do become ONE by joining (copulating).
The original description above of a man and his wife joining within a marriage situation ... implies the natural reproduction of children is the expected purpose.
SECONDLY:
It would also be a sin to withhold off-spring to a spouse according to what is taught in the OT about the sons of Judah and their sister-in-law. Judah's son, her husband, had died without leaving her with a child. It was expected that Judah would give her as the wife to another of his sons and
that son would be expected to give her a child. For varied reasons each of the sons, who became her husbands, were not fulfilling their responsibility to her.
The last one was spilling his semen on the ground, because he did not want to give her children. A conclusion to all of this is ... if a man,
who is expected by his partner within a marriage to produce offspring by her...
were to withhold his semen...
whether through abstinence, or use of a condom, or by spilling it on the ground as happened in the OT story of Judah's son,
it is a sin.
IOW, both partners need to simultaneously and freely agree that a child is not their goal at the time of the marriage... or that they want to wait a specific amount of time and then have children. IOW ... have an agreement ahead of time.
If they marry saying that they don't want children at all, but then one spouse changes his/her mind later, but not the other ... I, personally don't feel that the one withholding will be sinning.
Yet, if they do become pregnant anyway even after using birth control and agreeing to no children, then they should honor God, the giver of life, regarding that conception and take the responsibility as the parents of
a new ONE coming from them.