Skandapurana 5.207.18

5.207.18

utpatsyate ravervaṃśe rāmarūpī janā rdanaḥ..
rāvaṇasya vadhārthāya mānuṣaṃ rūpamāsthitaḥ..
tasya pādasya saṃsparśādbhūyaḥ śuddhā bhaviṣyati.
tasmātpratīkṣya tāvattvamautsukyaṃ vraja putraka..
etatsamyaṅmayā jñātaṃ vatsa divyena cakṣuṣā..18..

Janārdana in the form of Rāma will be born in the Solar dynasty, / assuming a human form for the sake of slaying Rāvaṇa. / By the touch of his foot she will become pure again. / Therefore, wait until then, my son, and be patient! / This has been rightly known by me, my child, through the divine eye." // 18