The meaning of this sentence is that if the righteousness is sufficient within, the evil qi cannot offend, and the accumulation of evil qi is due to the lack of righteousness.
From: "Huangdi Nei Jing Su Wen Commentary on Fever Diseases", a medical work from the pre-Qin to Han dynasties, the original text is as follows:
Qi Bo said: Where evil comes together, the Qi will be deficient. If the yin is deficient, the yang will join in, so when there is little qi, it will be hot and cause sweating. Yellow urine means there is heat in the abdomen. Those who cannot straighten their stomachs have disharmony in their stomachs. When the patient is biting, the cough becomes severe and the upper part presses the lungs. For those with water vapor, slight swelling will first appear under the eyes.
Translation:
Qi Bo said: The accumulation of evil spirits is due to the lack of righteousness. When kidney yin is insufficient, yang evils take advantage of the deficiency and gather together, resulting in shortness of breath, constant fever, sweating, and yellow urine. This is because of internal heat and cannot lie on one's back, which is caused by disharmony in the stomach. Coughing gets worse when lying on your back, because water vapor is forced upward into the lungs. For patients with water vapor, signs of slight swelling can be seen at the eyes.
Extended information:
The "Huangdi Neijing" is divided into two parts: "Lingshu" and "Suwen". It is the earliest medical classic in China and one of the four classics of traditional medicine.
The "Huangdi Neijing" is a comprehensive medical book. It establishes the "Yin-Yang and Five Elements Theory", "Pulse Theory", "Zangxiang Theory" and "Meridians" in traditional Chinese medicine based on Huang-Lao Taoist theory. Theory" and other theories discuss medicine from a holistic perspective, and their basic materials come from ancient Chinese people's long-term observation of life phenomena, a large amount of clinical practice and simple anatomical knowledge.
The "Huangdi Neijing" lays the foundation for understanding human physiology, pathology, diagnosis and treatment. It is a medical work with great influence in China and is known as the ancestor of medicine.
Reference material: Baidu Encyclopedia - Huangdi Neijing Suwen·Comments on Fever