As-salamu `alaykum wa rahmatullahi wa barakatuh,
As parents, it is natural to feel concern for our children, but that does not mean that we have to take seriously everything that we are told. Some information is pragmatic, but without consideration of spiritual aspects, this makes pragmatism only a useful tool, not a means to an end. Other information can be purely superstitious, but this does not make it null and void. One should be mindful of the state of mind of the person who is conveying the information, and ascertain the intention behind conveying that information.
In traditional societies (including Muslim societies), and in natural parenting, it is considered unnatural to have one’s child sleep on one own. Ones child comes into the world, often kicking and screaming into a reality that they do not know. The person they come into the world through is their mother, for whom the smell of is a comforting odor. This can also apply to significant others, like the father.
Suckling a child, cuddling them and being tactile as well as via one’s voice, are ways in which a child bonds with one’s mother, and/or significant others. This is the nature of sleep at that tender age and is how a child feels secure in this strange world that he/she has entered into.
However, on what basis this person spoke to your husband knows that your daughter can be harmed by jinn should be questioned.
“Abdullah b. Mas’ud reported that Allah’s Messenger (may peace be upon him) said: There is none amongst you with whom is not an attache from amongst the jinn (devil). They (the Companions) said: Allah’s Messenger, with you too? Thereupon he said: Yes, but Allah helps me against him and so I am safe from his hand and he does not command me but for good” (Al Bukhari 39: 6757).
Knowing that we are all susceptible might help, but in terms of ruling, you are well advised to re-submit your question to Ask the Scholar.
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