Is one sinful if he throws away a gift from someone he dislikes, especially if the gift is something edible or drinkable, such as Zamzam water, fearing that it might contain something detestable, knowing that he accepts it in front of the giver?

The Prophet, peace and blessings be upon him, guides his Ummah to exchange gifts, for it increases love and removes rancor. A Muslim must accept gifts from his brethren, and if he does not need them, he may gift them to others, provided they are pure and free from harm, especially if they are relatives or neighbors. If he doubts them or fears harm from them, he may return them after showing courtesy and thanking them, in order to preserve affection. Scholars have stipulated the permissibility of returning a gift if one fears obligation or harm. One should have a good opinion of Muslims. However, if one fears or strongly suspects that there is harm in their gifts, he should not accept them and return them graciously, because there is no harm or reciprocating harm, and wasting money is impermissible, and so that they do not have an obligation over him or compel him to reciprocate for something he did not benefit from. This strong suspicion must be based on objective reasons, not mere illusions and delusions.