1 As thy day thy strength shall be,
Is the promise given thee
By the Father, God and Friend,
Who relief will ever send,
As in humble fervent prayer
Thou dost all thy need declare.
2 As thy day thy strength shall be.
Think not what may happen thee!
Leave the future in his care
Who guards all things ev’rywhere,—
Guides the earth upon its way
By His universal sway.
3 Think’st thou he’ll forget his child
Journeying through the dang’rous wild
Of this world’s entangling snares,
Toiling ‘mid depressing cares?
Ev’ryday of life thou’lt see
AS thy day thy strength shall be.
Source: The Helper in Sacred Song: for Sunday-schools, churches, and devotional services #147
"The New Year's Bells were ringing in St. Nicholas' Church close to our Rectory (Worcester). I was sleeping with my sister Maria; she roused me to hear them, and quoted the text, ‘As thy days thy strength shall be,' as a New Year's Motto. I did not answer, but presently returned it to her in rhyme (the two first verses, I think). She was pleased, so I finished it the next day and gave it her. The last verse, with a slight alteration, was placed by my cousins on Aunt Izard's tomb, 1868, thus:— "Now thy days on earth are past, Christ hath called thee home at last" [Havergal Manuscript]This hymn is not in common use in Great Britain, but it has been adopted by various American compilers, and is given in Hymns and Songs of Praise, N. Y., 1874, Songs of Christian Praise, N. Y., 1880, &c. -- John Julian, Dictionary of Hymnology (1907)