When he (the eater) offers the fifth oblation, he offers it saying - ‘Udānāya svāhā’ (I offer this as an oblation to udāna). With this, udāna becomes pleased.
When udāna is pleased, the organ of touch is pleased; the organ of touch being pleased, air is pleased; when air is pleased, space is pleased; when space is pleased, whatever is under the control of air and space is pleased. Then when that is pleased, the eater derives pleasure from his children, from his animals, from an abundance of food, from physical strength, and from his good life and scholarship.