Valmiki Ramayana Bala Kanda Sarga 12 Shloka 1

तत: afterwards, बहुतिथे काले after a lapse of long time, सुमनोहरे charming, कस्मिंश्चित् some time, वसन्ते spring season, समनुप्राप्ते having arrived, राज्ञ: for the king, यष्टुम् to perform sacrifice, मन: अभवत् desire arose.

After a long time, at the advent of charming spring a desire arose in the mind of the king (Dasaratha) to perform the sacrifice. Dasaratha requests Rsyasringa to perform the sacrificethe priests order him to procure necessary materials and to release the sacificial horse--Dasaratha orders his ministers to get the preparations done.