Overnight separation from mother

Ok so my baby girl just turned 6 months old and her father who lives in another state keeps hounding me to let her spend the night with him and I’m just not comfortable with it. She’s been with me everyday since she was born and he thinks I’m being selfish because I won’t let him take her. Am I wrong for this or is it really ok for him to take her overnight??? Someone please help me this argument has ruined our relationship...