You clearly have not read the bible if you think it says that only.
> Thus saith the LORD of hosts, I remember that which Amalek did to Israel...
Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass.
> Thus saith the LORD of hosts, I remember that which Amalek did to Israel... Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass.