The meaning of two sentences is: heaven (that is, nature) is strong, and accordingly, a gentleman should behave like heaven, strive for self-improvement, be resolute and vigorous, and not be lazy; The earth absorbs sunlight and nourishes everything. A gentleman should increase his morality and set an example. It means that the universe keeps running, and people should follow the example of heaven and earth and move forward forever.
Later, Tsinghua University's motto was "Strive for Self-improvement, Be Virtuous and Carry Things".