Is the act of a mother placing candy under the head of a newborn and presenting it to an older child as a gift from his sibling considered a lie that teaches him wrong behavior, and what is the correct action to avoid lying and address the child's jealousy?

Lying is generally impermissible. However, scholars have permitted the use of tawriyah (ambiguous speech) and ma'arid (euphemisms) out of necessity, for a benefit, or to avert harm, as Umm Sulaym did with Abu Talhah. A woman can use tawriyah with her child to solve the problem of jealousy by saying to him, "This gift is from your brother," if the gift is indeed in his possession. She should not say, "Your brother gave it to you," as that would be an outright lie.