“The dog padded along beside him in blissful anticipation. It is lovely to be going home. And whenever she was a few yards ahead of her master, she would halt and look back at him with eyes full of an unwavering faith, then return to him in a big curve. Her reverence for her master was so great that she did not presume even to walk ahead of him. A dog finds in a man the things it looks for. He leaned into the gusts of driven snow, leading Blesi by the reins and casting an occasional glance at his dog – poor little thing, lousy and wormy, but where is fidelity to be found if not in those brown eyes – where the loyalty that nothing can subvert? Misfortune, dishonor, the pricks of conscience, nothing can quench this fire – poor little bitch, in her eyes Bjartur of Summerhouses must always be highest, greatest, best; the incomparable. Man finds in the eyes of a dog the things he looks for.”  –Halldor Laxness, Independent People

According to The Phrase Finder, “man’s best friend” first appeared in this 1820 poem which actually compares dogs unfavorably with horses (italics mine):

THE HORSE.
When, the fatigues of business past,
We find the wish’d repose at last,
The affections of the soul, in turn,
Will with their native ardour burn,
i> And various objects claim the care
Of men, wbat’er their natures are;
Exclusive of the love they feel
To friends and to the Commonweal.
The animated world affords
Affection’s wish exhaustless hoards
Of pleasures pure, which tone the mind
To joys and sympathies refined:
And some there are who praise the thrush
Whose dulcet notes their sorrows hush;
Some, Philomela’s plaintive lay,
In distance dying soft away;
Some at the linnet’s rejoice,
Or love the robin’s form and voice;
But most whom songsters please are fram’d
Like them with souls completely tam’d;
Columbia’s bird disdains the song,
To deeds, not sound, his pow’rs belong,

His voice but echoes through the sky
In the wild scream of victory.
Full many sons of men have been,
Who in the lion’s port and mien,
In his proud form and lordly eye,
Have seen th’ impress of majesty;
And so they are—his voice is heard,
And all his loyal subjects, scar’d,
Crouch close and closer in their lairs,
And forth and front him no one dares;
The elephant to toil inur’d,
Has much sincerer praise secured,
For gratitude his bosom fires
With zeal, that but with life expires;
His clumsy frame submits to schooling,
He loves the hand that’s o’er him ruling;
The Reindeer thro’ the trackless wastes
Of winter snows, his journey hastes;
He shall not lose his praise, for there
Where Lapland’s cliffs rise bleak and bare,
His worth is thought beyond compare.
The faithful dog —why should 1 strive
To speak his merits, while they live
In every breast, and man’s best friend
Does often at his heels attend.
But still this generous friend will be
Most faithful both to you and me;
Let but the pointer spring the game,
All other joys to him are tame,
And following a stranger’s gun,
This faithful friend will often run;
And when the dire disease assails,
At whose attack his nature fails,
The kindest masters shun his sight,
For dogs when mad will surely bite.
The generous steed my praise deserves,
Who toils so long and truly serves:
Oh! could I mark his glancing eye
Which speaks of conscious dignity,
His ample chest, his flowing mane,
And not to him the prize ordain?
When borne along in thickest fight,
Which must the coward soul affright,
Who proudly stems the battle tide?
The noble horse—the warrior’s pride.
If in the appearance, and the face
Of men, we oft their tempers trace;
If we pronounce his guilt most clear
Whose features blanch with deadly fear;

It the base dog, who sneaks away
With trembling limbs from hostile fray,
Is deemed a recreant, then compare
The horse’s form and noble air,
And fix your admiration there. )

The New-York literary journal, and belles-lettres repository, v.4, 1820/21