To resist - That is, they were not able to “answer” his arguments.
The wisdom - This properly refers to his knowledge of the Scriptures; his skill in what “the Jews” esteemed to be wisdom - acquaintance with their sacred writings, opinions, etc.
And the spirit - This has been commonly understood of the Holy Spirit, by which he was aided; but it rather means the “energy, power,” or “ardor” of Stephen. He “evinced” a spirit of zeal and sincerity which they could not withstand; which served, more than mere argument could have done, to convince them that he was right. The evidence of sincerity, honesty, and zeal in a public speaker will often go further to convince the great mass of mankind, than the most able argument if delivered in a cold and indifferent manner.