1 Thessalonians 2:9

2:9 For you recall, brothers and sisters, our toil and drudgery: By working night and day so as not to impose a burden on any of you, we preached to you the gospel of God.

1 Thessalonians 3:5

3:5 So when I could bear it no longer, I sent to find out about your faith, for fear that the tempter somehow tempted you and our toil had proven useless.