What was the extent of Yitzchak's greatness (wealth)?*
Why does the Pasuk repeat the word 'great' three times?
Ba'al ha'Turim: This corresponds to three Berachos at the Akeidah - "Ki Varech Avarechecha... v'Hisbarchu b'Zaracha" (22: 17-18).
Malbim: "Va'Yigdal ha'Ish" teaches that the Berachah was due to him, and not due to the land or the grain. "Haloch v'Gadel" - he never suffered a loss; "Ki Gadal Me'od" - unlike one who succeeds due to Mazal, who later descends.
Ha'amek Davar: "Va'Yigdal ha'Ish" - in wealth. "Haloch v'Gadel" - every day he increased wealth. "Ki Gadal Me'od" - more than normal, even for kings. This was a sign for his descendants, that it will be so, even if they will be strangers subjected to Nochri kings, like Yitzchak was under Avimelech.
QUESTIONS ON RASHI
Rashi writes: "He had grown exceedingly great - [People] would say, '[We prefer] the manure of Yitzchak's mules, and not the gold and silver of Avimelech!'" Why expound this way?
Gur Aryeh: The verse has already stated, "He grew continuously greater;" so this phrase appears superfluous. It means that Yitzchak's assets grew to the greatest possible degree. Rashi does not refer only to the net worth of his property, but to the blessing and success that it enjoyed. Even the manure of Yitzchak's mules experienced blessing, (despite the fact conceptually mules are unfit for blessing, as they cannot reproduce).
Rashi writes: People were saying, 'Better the dung of Yitzchak's mules (Pereidos)....' But it was only later in history that Anah brought mules into the world (see Rashi to Bereishis 36:24)!
Moshav Zekenim #1: Anah initiated white mules, whose Eimah (fear) is on people, so they are called Yemim.
Moshav Zekenim #2: Pereidah is an expression of increase of young animals and birds.
Riva: There were mules before Anah; he found a way to produce more through crossbreeding.