2 Corinthians 11:30
“If I must needs glory, I will glory of the things which concern my weakness.”
Do you see that he no where glories of miracles, but of his persecutions and his trials? For this is meant by “weaknesses.” And he shows that his warfare was of a diversified character. For both the Jews warred upon him, and the Gentiles stood against him, and the false brethren fought with him, and brethren caused him sorrow, through their weakness and by taking offense:— on every side he found trouble and disturbance, from friends and from strangers. This is the special mark of an Apostle, by these things is the Gospel woven.
Source: Homilies on Second Corinthians (New Advent)