Albert Barnes Commentary 1 Corinthians 1:22

"Seeing that Jews ask for signs, and Greeks seek after wisdom:" — 1 Corinthians 1:22 (ASV)

For the Jews require a sign—that is, a miracle, a prodigy, an evidence of Divine interposition. This was the characteristic of the Jewish people. God had manifested himself to them by miracles and wonders in a remarkable manner in past times, and they greatly prided themselves on that fact. They always demanded such evidence when any new messenger came to them professing to be sent from God. This propensity they often showed in their interactions with the Lord Jesus, Matthew 12:38; Matthew 16:1; Mark 8:11; Luke 11:16; Luke 12:54–56.

Many manuscripts, instead of "sign" here in the singular, read signs in the plural, and Griesbach has introduced that reading into the text. The meaning is nearly the same. It indicates that it was characteristic of the Jews to demand the constant display of miracles and wonders.

Furthermore, it is implied here, I think, from the apostle's reasoning, that they believed receiving such signs as a people would secure their salvation, and they therefore despised the simple preaching of a crucified Messiah. They expected a Messiah who would come with a display of stupendous signs and wonders from heaven (as seen in Matthew 12:38 and the other passages mentioned above). They looked for displays of amazing power in his coming and anticipated that he would deliver them from their enemies by mere power. Consequently, they were greatly offended by the simple doctrine of a crucified Messiah, 1 Corinthians 1:23.

And the Greeks, etc. Perhaps this means Gentiles in general, in opposition to the Jews. (See Barnes on Romans 1:16).

It was, however, particularly the characteristic of the Greek philosophers. They seek systems of philosophy and religion that depend on human wisdom, and they therefore despise the gospel.