'Strong' in the Bible

For, His letters, they say, are weighty and strong; but his bodily presence is weak, and his speech of no account.

Wherefore I take pleasure in weaknesses, in injuries, in necessities, in persecutions, in distresses, for Christ's sake: for when I am weak, then am I strong.

For we rejoice, when we are weak, and ye are strong: this we also pray for, even your perfecting.