John Calvin Commentary Philippians 4:10

"But I rejoice in the Lord greatly, that now at length ye have revived your thought for me; wherein ye did indeed take thought, but ye lacked opportunity." — Philippians 4:10 (ASV)

But I rejoiced He now expresses his gratitude to the Philippians, so that they would not regret their generosity, as often happens when we believe our services are despised or considered worthless. They had sent him supplies by Epaphroditus to relieve his need; he declares that their gift had been acceptable to him, and he says that he rejoiced because they had revived their concern for him.

The metaphor is borrowed from trees, whose strength is drawn inward and lies hidden during winter, and then flourishes in spring.

But immediately afterward, adding a correction, he clarifies what he had said, so that he might not seem to be rebuking their past negligence. He says, therefore, that they had also previously been concerned about him, but that the circumstances at the time had not permitted them to relieve him sooner with their kindness. Thus, he attributes the delay to a lack of opportunity.

I understand the phrase ἐφ᾿ ᾧ᾿ as referring to Paul himself, and that is its correct meaning, and also more consistent with the context of Paul’s words.