Heat the oil in a heavy large skillet over medium heat. Add the garlic and red pepper flakes, and saute until the garlic is golden, about 1 minute. Reduce heat to medium-low. Add the broccoli rabe and toss to coat. Add the reserved cooking water, the raisins, and cook until the broccoli rabe is heated through and the stems are tender, about 4 minutes. Season with salt, to taste. Just before serving, toss the mixture with the pine nuts.