Like red soil with rain

The hero assures his beloved who is apprehensive about the future of their relation. He says that they will be united in love forever. He relates beautifully something happening in nature and uses it as a simile for their love. What does he take from the nature to symbolize their relation?
Lets see the beautiful kurinji thinai poem from kurunthogai, one of the Eight Anthologies of sangam poems. The name of the poet is unknown. Hence he is called by the pseudonym, "Sembulap peyaneeraar" (செம்புலப் பெயனீரார்) where the words are taken from the poem itself. The poem depicts the words spoken by the hero to the heroine.

குறுந்தொகை 40
"யாயும் ஞாயும் யாராகியரோ?
எந்தையும் நுந்தையும் எம்முறைக் கேளிர்?
யானும் நீயும் எவ்வழி அறிதும்?
செம்புலப் பெயல்  நீர் போல
அன்புடை நெஞ்சம் தாம் கலந்தனவே"

Kurunthokai 40
"yaayum ngyaayum yaaraagiyaro?
endhaiyum nundhaiyum emmuraik kelir?
yaanum neeyum evvazhi aridhum? 
sembulap peyal neer pola
anbudai nenjam thaam kalandhanave"

Poem meaning:
My mother and your mother, who are they to each other? My father and your father, how are they related? Me and you, how we do know each other? Similar to the red soil mixed with water, hearts earnest in love became one.

Words meaning: yaayum - my mother, ngyaayum - your mother, yaar - who, aagiyaro - what relation are they to each other, endhaiyum - my father, nundhaiyum - your father, emmurai - which way, kelir - relative, yaanum - me, neeyum - you, evvazhi - how, aridhum - know, sembulap - mixed with red soil, peyal - rain, neer - water, pola - like, anbudai - loving, nenjam - heart/mind, thaam kalandhanave - became one


Description: Hero and heroine are in love. The heroine is worried if their love will succeed. So the hero assures her that they would be united forever and that they would be inseparable. He says though they are not of kin, maternally or paternally, their hearts fell in love naturally. He says that their loving hearts became one like the rain water mixed with red soil.

My English version:
"My mother and yours, what kinship are they?
My father and yours, how related are they?
You and I, how do we know each other?
Like red soil blending with rain water
Earnest hearts in love became one forever"