Verses with the word strengthen in the New Testament (3 verses):

Luke 22:32
But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren.

1 Peter 5:10
But the God of all grace, who hath called us unto his eternal glory by Christ Jesus, after that ye have suffered a while, make you perfect, stablish, strengthen, settle you.

Revelation 3:2
Be watchful, and strengthen the things which remain, that are ready to die: for I have not found thy works perfect before God.