Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(He knoweth all that is before them) of the matter of the Hereafter (and all that is behind them) of the matter of the life of this world, (and unto Allah all things) the consequence of all things (are returned) in the Hereafter.
He knows that which is before them and that which is behind them, in other words, what they have offered [in the way of deeds] and what they have left behind, and what they have done and what they will do next; and to God all matters are returned.
(He knows what is before them, and what is behind them. And to Allah return all matters.) He knows what will happen to His Messengers and the Message He sent them with, for none of their affairs are hidden from Him. He says:
(O Messenger! Proclaim which has been sent down to you from your Lord. And if you do not, then you have not conveyed His Message. Allah will protect you from mankind) 5:67.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
In continuation of the refutation of shirk, Allah has taken two kinds of the most revered of "deities" to show their real status, as if to say, "The angels and the Prophets whom you have set up as deities are mere Messengers of Allah. Allah has chosen them to convey His Messages to human beings and this does not make them God or partners in His Godhead.
The Qur'an employs this sentence to refute the creed of the mushriks in regard to intercession, as if to say, "You imagine that angels, prophets, saints,and the like can intercede with Allah on your behalf and therefore you worship them. You are absolutely wrong, for none of your deities knows what is good for you and what is not: Allah alone hears everything, sees everything and knows everything. Therefore He has not given the right of intercession and recommendation to anyone except when He Himself is pleased to give such permission."
This is to impress upon them that every affair and every matter, big or small, is presented before Allah for a decision. Therefore you should not invoke anyone else than Allah, for all others are utterly helpless and powerless and cannot even fulfill their own desires and needs.