“Now Isaac sowed in that land and reaped in the same year a hundredfold. And the LORD blessed him, and the man became rich, and continued to grow richer until he became very wealthy; for he had possessions of flocks and herds and a great household, so that the Philistines envied him.” Gen. 26:12-14
Abraham had received plenty of good things, including oxen, donkeys, and servants, from both Pharaoh (Gen. 12) and Abimelech (Gen. 20). The only thing Isaac receives is the king’s protection, however Isaac still goes on to amass a multitude of these things on his own. As Robert Alter points out, Abraham had many blessings given to him, but Isaac’s were the fruit of his own labor. They were also blessings from God of course, for staying and sojourning in Gerar (v. 3).
To the Jewish reader, it may seem odd that Isaac “counted his blessings” with the crop he reaped, as Bereshis Rabbah 64:6 says not to look for blessings in things that can be counted, but rather things that are hidden. Thus Rashi says the field was estimated for purposes of tithing to the poor.
Rashi also notes in the original Hebrew v. 12 reads “in that land… in that year…” which was written to underscore that it was not the best land to farm, and not a particularly good crop year, yet we see Isaac’s blessings still overflowed.
The Jewish Study Bible notes that the reference to the Philistines in v. 14 is likely anachronistic, as they did not arrive in Canaan until 1200 B.C.