Two are better than one, because they have a good return for their labor: If either of them falls down, one can help the other up. But pity anyone who falls and has no one to help them up. Also, if two lie down together, they will keep warm. But how can one keep warm alone? Though one may be overpowered, two can defend themselves. A cord of three strands is not quickly broken.

The Bible (The Old Testament) (14th - 2nd C BC) Judeo-Christian sacred scripture [Tanakh, Hebrew Bible], incl. the Apocrypha (Deuterocanonicals)

Ecclesiastes 4:9-12 [NIV (2011 ed.)]
    (Source)

Alternate translations:

Two are better than one; because they have a good reward for their labour. For if they fall, the one will lift up his fellow: but woe to him that is alone when he falleth; for he hath not another to help him up. Again, if two lie together, then they have heat: but how can one be warm alone? And if one prevail against him, two shall withstand him; and a threefold cord is not quickly broken.
[KJV (1611)]

Better two than one by himself, since thus their work is really profitable. If one should fall, the other helps him up; but woe to the man by himself with no one to help him up when he falls down. Again: they keep warm who sleep two together, but how can a man keep warm alone? Where one alone would be overcome, two will put up resistance; and a threefold cord is not quickly broken.
[JB (1966)]

Two are better off than one, because together they can work more effectively. If one of them falls down, the other can help him up. But if someone is alone and falls, it's just too bad, because there is no one to help him. If it is cold, two can sleep together and stay warm, but how can you keep warm by yourself? Two people can resist an attack that would defeat one person alone. A rope made of three cords is hard to break.
[GNT (1976)]

Two are better off than one, in that they have greater benefit from their earnings. For should they fall, one can raise the other; but woe betide him who is alone and falls with no companion to raise him! Further, when two lie together they are warm; but how can he who is alone get warm? Also, if one attacks, two can stand up to him. A threefold cord is not readily broken!
[JPS (1985)]

Two are better than one because they have a good reward for their toil. For if they fall, one will lift up the other, but woe to one who is alone and falls and does not have another to help. Again, if two lie together, they keep warm, but how can one keep warm alone? And though one might prevail against another, two will withstand one. A threefold cord is not quickly broken.
[NRSV (1989 ed.)]