Confusion about a stanza from Rudyard Kipling

Following is the stanza:

Teach us delight in simple things,
And mirth that has no bitter springs;
Forgiveness free of evil done,
And Love to all men 'neath the sun!

What does second line and third line mean? And does the last line mean love to all people who work hard under the harsh sun?

A brief explanation will suffice.

(I hope that this is not a subjective question! Also, please change the tag; my reputation is not quite enough to create new one.)

"Bitter springs" means, basically, "springing from something bitter." So the second line means: may we learn to not be happy because of others' misfortunes.

"Forgiveness free of evil done" means that we'll forgive those who wrong us, and never remember again the evil they did. (Sort of the opposite of "I may forgive, but I'll never forget.")

In the last line, "under the sun" means "everyone in the world" - the expression is borrowed from Ecclesiastes (1:3).

Teach us delight in [...] mirth that has no bitter springs

I believe this means "Teach us to enjoy humor that is does not have a basis in (buoyed up by) cruelty or unkindness.

Teach us delight in [...] forgiveness free of evil done

I believe that this means "Teach us to forgive others even of the most trivial grievances". (I am not convinced of this, though, as I do not know why this would be suggested as either unlikely or desirable.)

I believe the last line, "love to all men 'neath the sun" is simply saying to love everyone, as we are all underneath the sun (even when indoors). I do not think that there is any implication that they must be outdoor laborers.

A lot of poetry is will mean different things to different people. Much of this poem is a prayer. Here's how I interpret the lines you ask about:

And Mirth that has no bitter springs

We wish for joy without accompanying pain.

Forgiveness free of evil done

Allow mankind to be able to express love and forgiveness to each other without first suffering the offenses that would need to be forgiven.

And Love to all men 'neath the sun.

This is love for everyone, not just those that work in a field, for the sun shines on all the earth. It's a lovely poem.

"Mirth that has no bitter springs." Teach us to delight in happiness that is not derived from others' unhappiness.

"Forgiveness free of evil done." Teach us to forgive others for the evil they do, without retribution or restitution (free, not earned). Free is modifying forgiveness, so it is "free forgiveness", not "free of evil".

"All men 'neath the sun." Every person on the earth - common idiom. Not relating to laborers.