Valmiki Ramayana Bala Kanda Sarga 73 Shloka 28

महाभागा highly fortunate, पतिव्रता devoted, faithful and loyal wife, सदा always, छाया इव like shadow, अनुगता follows, इति thus, उक्त्वा having spoken, राजा king, तदा then,मन्त्रपूतम् sanctified with mantra, जलम् water, प्राक्षिपत् released.

By being a devoted wife this highly fortunate Sita would always follow you like a shadow". Thus spoken, he sprinkled the water sanctified with mantras (on them).