Allah says:

[وَلاَ يَمْلِكُ الَّذِينَ يَدْعُونَ مِن دُونِهِ]

(And those whom they invoke instead of Him have no power) means, the idols and false gods.

[الشَّفَـعَةَ]

(of intercession) means, they are not able to intercede for them.

[إِلاَّ مَن شَهِدَ بِالْحَقِّ وَهُمْ يَعْلَمُونَ]

(except for those who bear witness to the truth knowingly, and they know.) This means, but the one who bears witness to the truth has knowledge and insight, so his intercession with Allah will avail, by His leave.