Mark 7:25-30 (ESV)
25 But immediately a woman whose little daughter was possessed by an unclean spirit heard of him and came and fell down at his feet. 26 Now the woman was a Gentile, a Syrophoenician by birth. And she begged him to cast the demon out of her daughter. 27 And he said to her, “Let the children be fed first, for it is not right to take the children’s bread and throw it to the dogs.” 28 But she answered him, “Yes, Lord; yet even the dogs under the table eat the children’s crumbs.” 29 And he said to her, “For this statement you may go your way; the demon has left your daughter.” 30 And she went home and found the child lying in bed and the demon gone.
"Some mercies are not given to us except in answer to importunate (bold, persistent) prayer. There are blessings which, like ripe fruit, drop into your hand the moment you touch the bough. But there are others which require you to shake the tree again and again, until you make it rock with the vehemence of your exercise, for only then will the fruit fall down." -- Spurgeon