Isaiah 35

Isaiah wrote of the commandment -

"Strengthen ye the weak hands, and confirm the feeble knees.
4 Say to them that are of a fearful heart, Be strong, fear not: behold, your God will come with vengeance, even God with a recompence; he will come and save you." (Old Testament | Isaiah 35:3 - 4)

As we reach out, as we open our mouths, as we strenghten weak hands and feeble knees, the promise is -

"...the ransomed of the LORD shall return, and come to Zion with songs and everlasting joy upon their heads: they shall obtain joy and gladness, and sorrow and sighing shall flee away." (Old Testament | Isaiah 35:10)