The Prophet (may Allah's peace and blessings be upon him) encourages us to kill geckos. He informs us that anyone kills it with the first blow will have one hundred good deeds written for him; and anyone kills it with the second blow will have less than that (written for him); and whoever kills it with the third blow will have less than that (written for him). The wisdom behind killing geckos is that it was blowing into the fire in which Ibrahīm (peace be upon him) was thrown, and it is harmful and poisonous.