《黄帝内经·素问·离合真邪论》
治疗时应在吸气时进针，进针时勿使气逆，进针后要留针静侯其气，不让病邪扩散；当吸气时转捻其针，以得气为目的；然后等病人呼气的时候，慢慢地起针，呼气尽时，将针取出。这样，大邪之气尽随针外泄，所以叫做泻。
吸则内针，无令气忤，静以久留，无令邪布。吸则转针，以得气为故。候呼引针，呼尽乃去，大气皆出，故命曰泻。
When treating, one should pierce the needle at the moment of inhalation. While piercing, don't let the qi reverse, and after piercing, leave the needle and wait for the qi to calm down. Don't let the evil qi diffuse; when the qi is inhaled, twist the needle to achieve the purpose of leading the qi; then, when the patient exhales, slowly withdraw the needle, and when exhalation is complete, remove the needle. In this way, the evil qi will be drained out with the needle, so it is called purgation.