1On one occasion the Blessed One was dwelling among the Magadhans at the Maṇimalaka Shrine, the haunt of the yakkha Maṇibhadda. Then the yakkha Maṇibhadda approached the Blessed One and in the Blessed One's presence recited this verse:

1Ekaṁ samayaṁ bhagavā magadhesu vihārati maṇimālike cetiye maṇibhaddassa yakkhassa bhavane. Atha kho maṇibhaddo yakkho yena bhagavā tenupasaṅkami; upasaṅkamitvā bhagavato santike imaṁ gāthaṁ abhāsi: 

2v.812 "It is always good for the mindful one,
The mindful one thrives in happiness.
It is better each day for the mindful one,
And he is freed from enmity."[n.570] Spk glosses sukham edhati in pāda a as sukhaṁ paṭilabhati, "obtains happiness." CPD points out (s.v. edhati) that this interpretation is probably a misunderstanding stemming from the supposition that sukham is a direct object of the verb rather than an adverbial accusative. The original meaning appears in the commentarial gloss on the expression sukhedhito as sukhasaṁvaddhito. See too EV I, n. to 475.
Spk glosses suve seyyo in pāda c as suve suve seyyo, niccam eva seyyo; "It is better morrow upon morrow, it is always better."

2"Satīmato sadā bhaddaṁ,
satimā sukhamedhati;
Satīmato suve seyyo,
verā ca parimuccatī"ti.

The Blessed One:

3v.813 "It is always good for the mindful one,
The mindful one thrives in happiness.
It is better each day for the mindful one,
But he is not freed from enmity.

3"Satīmato sadā bhaddaṁ,
satimā sukhamedhati;
Satīmato suve seyyo,
verā na parimuccati.

4v.814 "One whose mind all day and night
Takes delight in harmlessness,
Who has lovingkindness for all beings—
For him there is enmity with none."[n.571] Spk: Ahiṁsaya, "in harmlessness," means "in compassion and in the preliminary stage of compassion" (Spk-pṭ: that is, the access to the first jhāna produced by the meditation on compassion). Mettaṁ so, "who has lovingkindness," means "he (so) develops lovingkindness (mettaṁ) and the preliminary stage of lovingkindness." [Spk-pṭ: He (so) is the person developing meditation on compassion.]
Evidently Spk and Spk-pṭ take so in pāda c to be the demonstrative counterpart of yassa in pāda a, with an implicit transitive verb bhāveti understood. While the exact meaning of mettaṁ so (or mettaṁso) is problematic, I prefer to take pāda c as an additional relative clause, the relatives being resolved only in pāda d by the clearly demonstrative tassa. Spk offers an alternative interpretation of mettaṁso as a compound of mettā and aṁsa, glossed as koṭṭhāsa, "portion": mettā aṁso etassā ti mettaṁso; "one for whom lovingkindness is a portion (of his character) is mettaṁso." Mp IV 71,9 glosses mettaṁso: mettāyamanacittakoṭṭhāso hutvā; "having become one for whom a loving mind is a portion"; see too It-a I 95,13–15. Brough remarks that mitrisa (in G-Dhp 198) "appears to have been interpreted by the Prakrit translator as equivalent to (Skt) maitri asya" (Gāndhāri Dharmapada, p. 242, n. 198).
Spk-pṭ: Because of his own hating mind someone might nurture enmity even towards an arahant who lacks meditation on lovingkindness and compassion. But no one could nurture enmity towards one who is endowed with liberation of mind through lovingkindness and compassion. So powerful is the meditation on the divine abodes (evaṁ mahiddhikā brahmavihāra-bhavanā).

4Yassa sabbamahorattaṁ,
ahiṁsāya rato mano;
Mettaṁso sabbabhūtesu,
veraṁ tassa na kenacī"ti.