How we cite our quotes: (Book.Chapter.Paragraph)
Quote #4
In general, if any branch of trade, or any division of labour, be advantageous to the publick, the freer and more general the competition, it will always be the more so. (2.2.52)
Smith makes no bones about it. More competition equals a better world and a wealthier nation. Period. He's told you why, and now it's time for you to nod and smile.
Quote #5
[By] directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. (4.2.9)
When everyone acts according to their self-interest, they'll produce whatever stuff the public wants the most. And if they do this, then the public's demands are always being addressed and satisfied to the best possible extent. That's why Smith believes there's an "invisible hand" that makes the market good for both buyers and sellers.
Quote #6
By discouraging improvement, the monopoly necessarily retards the natural increase of another great original source of revenue, the rent of land. (4.7.37)
Smith is worried that if some people control too much of a country's land, they won't be motivated to improve the land and make it more productive. That's why he wants there to be a lot of competition in the marketplace. People need to feel pressured to make their land more productive and profitable if the nation is going to become wealthier.