Mercury, when placed in the third house for Sagittarius Ascendant, has a special impact on the native's life. Mercury is considered a very influential planet in Vedic astrology and is referred to as the planet of intellect, communication, and business. Its effects vary depending on its placement in different houses of the birth chart.
In this particular case, since Mercury is placed in its friend sign state, it brings significant positive changes to the individual's life. The third house represents courage, communication skills, siblings and social network. Hence, natives with this placement are blessed with excellent communication skills which they use to their advantage in both personal and professional lives.
Moreover, Mercury being the lord of seventh (relationships/marital life) as well as tenth house (career), helps in balancing relationships at work or personal front effectively. These individuals are smart workers and always strive for perfectionism when it comes to their job or business-related matters. They possess excellent decision-making abilities and use their intellectual power to make informed decisions.
Mercury is also the natural karaka for fourth (home/family) and tenth house (career). Therefore, natives with this astrological combination have a significant impact on these two houses of their birth chart. They will take care of matters related to home & family very enthusiastically while maintaining an excellent balance between personal life and professional commitments.
The aspect of Mercury on ninth house signifies intellectual wisdom coupled with good fortune. Natives with this combination possess an inherent deep desire for knowledge acquisition that often leads them on journeys to acquire new knowledge regarding science philosophy or religion.
However, it is essential to note that despite being in a friendly disposition during its transit through the third house resulted from placing it here for Sagittarius ascendants does not lend well if afflicted by malefic planets such as Rahu/Ketu/Mars etc., The negative impact might result in mental restlessness leading up to a psychological breakdown causing damage to the individual's mental and emotional wellbeing.
In conclusion, Mercury placed in the third house for Sagittarius ascendants is a boon. Individuals blessed with this astrological combination are natural communicators with outstanding social skills. They possess an unmatchable intellectual prowess that helps them make informed decisions, reflecting their intelligence and precision at work. Possessing both the houses of career (tenth) and marital life/ partnership (seventh), they exhibit mastery in balancing their personal and professional lives. With an almost uncanny thirst for knowledge, aided by a healthy dose of good fortune, natives excel in acquiring wisdom from various sources of knowledge. Notably, awareness of afflictions from malefics such as Mars or Ketu is essential to avoid falling prey to its impact on the individual's mental & emotional well-being resulting in a significant meltdown.