This excerpt is taken from a classical text:
Shen Qu Ba Fa
化 象
Transformation Image
化象者，乃甲己日生人，在辰戌丑未月，天干有一己字合甲字，謂之甲己化土。
Transformation Image, is like a Jia Ji born person, in the month of Chen Xu Chou or Wei, having a Ji on the HS to combine with Jia, it's called Jia Ji transformation to Earth
喜行火運。
Favors going through Fire LP
如逢甲木生旺，逢化不成，反為不吉，己字中露出二甲字，為之爭合，有一個乙字露出，謂之妒合，均破格不成。
If Jia wood is born in ChangSheng or DiWang, then the transformation will not be successful, that is inauspicious, if there is one Ji between one Jia, it is called competing combination, if there's a Yi exposed, it is called jealousy combination, they are broken and unsuccessful structures.
又曰："化者，陰陽合化之意也。乃天地相停，五行均配。
Also: Transformation means it the pairing of Yin and Yang that transforms. That is Heaven and Earth equates, five elements are matching.
"經云："化內從局，運轉而成封帝側。
The classics says: "For Transformation, Internal and Follower Structure, when the Luck turns to be successful, one could be appointed to be someone close to the emperor"
"又曰："化象伏而平生碌碌, "謂干支相停者化，是看日時合化不合化。
Also: Transformation Qi that 'submits', one's life will be mediocre. It is said that when Stems and Branches are equal transformation happens, it is to be seen whether Day and Hour combine and transform or combine but do not transform.
玉井云："五氣有化象，須要純一清潔。化而或返，有貴有賤，化而不化，或壽或夭。
Yu Jing says: " The five Qi have transformation image, it must be pure and clean, transformed or inverted, there's noble and there's lowly, transform but does not transform, could be long-lived or short-lived.
"通玄論云： "乙旺庚從，庚旺乙從。日主無氣化有氣，方可用。若各無氣，不可用，如丁壬化木，生於春，則夫從妻生；生於冬，則妻從夫生，是謂化也。
Tong Xuan Lun says: "When Yi is prosperous, Geng will follow. The DM without Qi will transform to be with Qi, then only it is usable. If each are without Qi, they are both unusable. like Ding Ren transforming to wood, born in spring, the husband will follow his wife to engender; born in winter, the wife will follow her husband to engender, this is called transformation.
如甲戌甲寅癸巳戊午，戊癸化火，生於寅月，臨官於巳，旺於午，此化氣得時得位。
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Wu Gui Jia Jia
Wu Si Yin Xu
Wu and Gui transforms to Fire, ChangSheng in the month of Yin, LinGuan in the month of Si and DiWang at Wu, this transformation structure obtains the time and the place.
