Your God is only Allah, there is no God but Him. He has full knowledge of all things.
Musa was saying to them, "This is not your god. Your God is only Allah, the One Whom there is no true God except Him. Worship is not befitting to anyone except Him. For everything is in need of Him and everything is His servant.
Concerning the statement,
...
وَسِعَ كُلَّ شَيْءٍ عِلْمًا
He has full knowledge of all things.
The word `Ilm (knowledge) is in the accusative case for distinction. It means that He is the All-Knower of everything.
أَحَاطَ بِكُلِّ شَىْءٍ عِلْمَا
(Allah) surrounds all things in (His) knowledge. (65:12)
And He says,
وَأَحْصَى كُلَّ شَىْءٍ عَدَداً
And (He) keeps count of all things. (72:28)
Therefore,
لااَ يَعْزُبُ عَنْهُ مِثْقَالُ ذَرَّةٍ
Not even the weight of a speck of dust escapes His knowledge. (34:3)
He also says,
وَمَا تَسْقُطُ مِن وَرَقَةٍ إِلاَّحَبَّةٍ فِى ظُلُمَـتِ الاٌّرْضِ وَلاَ رَطْبٍ وَلاَ يَابِسٍ إِلاَّ فِى كِتَـبٍ مُّبِينٍ
Not a leaf falls, but He knows it. There is not a grain in the darkness of the earth nor anything fresh or dry, but is written in a Clear Record. (6:59)
And He says,
وَمَا مِن دَابَّةٍ فِي الاٌّرْضِ إِلاَّ عَلَى اللَّهِ رِزْقُهَا وَيَعْلَمُ مُسْتَقَرَّهَا وَمُسْتَوْدَعَهَا كُلٌّ فِى كِتَابٍ مُّبِينٍ
And no moving creature is there on earth but its provision is due from Allah. And He knows its dwelling place and its deposit. All is in a Clear Book. (11:6)
The Ayat that mention this are numerous.