9 Of these was this woman; therefore she was not refused, but only put off. “I am not sent,” says He, “but unto the lost sheep of the house of Israel.” And she was instant in her cries: she persevered, she knocked, as if she had already heard, “Ask, and receive; seek, and you shall find; knock, and it shall be opened unto you.” She kept on, she knocked. For so the Lord when He spoke these words, “Ask, and you shall receive; seek, and you shall find; knock, and it shall be opened unto you;” had also said before, “Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you;” that is, lest after despising your pearls, they should even ill use you. Cast not therefore before them what they despise.
Source: Sermons on Selected Lessons of the New Testament (New Advent)