John Calvin Commentary 1 Thessalonians 3:10

"night and day praying exceedingly that we may see your face, and may perfect that which is lacking in your faith?" — 1 Thessalonians 3:10 (ASV)

Praying beyond measure. He returns to an expression of his desire. For it is never allowable for us to congratulate people, while they live in this world, in such unqualified terms as not always to desire something better for them. For they are still on their journey: they may fall back, or go astray, or even turn back.

Hence Paul desires an opportunity to supply what is wanting in the faith of the Thessalonians, or, which is the same thing, completing in all its parts their faith, which was still imperfect. Yet this is the faith which he had previously highly praised. But from this we infer that those who far surpass others are still far distant from the goal. Hence, whatever progress we may have made, let us always keep in view our deficiencies (ὑστερήματα), that we may not be reluctant to aim at something further.

From this it also appears how necessary it is for us to give careful attention to doctrine, for teachers were not appointed merely to lead people to the faith of Christ in a single day or month, but for the purpose of perfecting the faith that has begun.

But as to Paul’s claiming for himself what he elsewhere declares belongs uniquely to the Holy Spirit (1 Corinthians 14:14), this must be restricted to the ministry. Now, as the ministry of a man is inferior to the efficacy of the Spirit and, to use the common expression, is subordinate to it, nothing is detracted from it.

When he says that he prayed night and day beyond all ordinary measure, we can gather from these words how diligent he was in praying to God, and with what ardor and earnestness he performed that duty.