In plain words
Yaśōdā longs: "As a young one born of a great, fine silver mountain runs on ahead, moṭumoṭu, in haste, and a young one of a dark mountain follows behind, lifting and setting down its steps, so, while his elder brother called Baladēva, whose fame the world studies and praises without end, runs on ahead, he goes after him to catch up: won't he walk his toddling walk?"