Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

Condoms could be used by a married couple. It would be lawful to sell to them.

On the contrary, condoms could also be used by unmarried people to commit unlawful acts. If one knows that they would be used for such, then it is unlawful to sell to them.

Ibn Hajar al-Haytami mentioned,

كل ما يعلم البائع أن المشتري يعصي به يحرم بيعه له

“That which the seller knows the buyer will sin with, selling it to him is unlawful.” (al-Fatawa v. 2, p. 270)

This applies when the buyer is a Muslim and likewise when a non-Muslim. And to highly suspect [ghalabat al-zann] that one will commit an unlawful act is sufficient to make the sale unlawful. (Ibid)

And Allah knows best.

Shafiifiqh.com Fatwa Dept.