Into each life a little rain must fall.
The strictly correct quote is:
Into each life some rain must fall.
Source: From the poem The Rainy Day by Henry Wadsworth Longfellow.
Can be found in the collection The Rainy Day Ballards.
Actual quote is from the penultimate line of the third stanza.
The Rainy Day
The day is cold, and dark, and dreary
It rains, and the wind is never weary;
The vine still clings to the mouldering wall,
But at every gust the dead leaves fall,
And the day is dark and dreary.
My life is cold, and dark, and dreary;
It rains, and the wind is never weary;
My thoughts still cling to the mouldering Past,
But the hopes of youth fall thick in the blast,
And the days are dark and dreary.
Be still, sad heart! and cease repining;
Behind the clouds is the sun still shining;
Thy fate is the common fate of all,
Into each life some rain must fall,
Some days must be dark and dreary.
This poem is in the public domain.
Comment: The misquote of “a little rain” is very common.
It is also performed as a song:
"Into Each Life Some Rain Must Fall" is a 1944 song performed as a duet by The Ink Spots, featuring Bill Kenny, and Ella Fitzgerald.”
See Wikipedia here.