Here are some verses from the Holy Quran concerning true and pure Imams:

It is Allah's wish to remove all blemish from you, O Ahlul-Bayt, and purify you with a perfect purification. (33:33)

Say, I ask no reward from you for it except the love of my kinsfolk. And whosoever does a good deed we add unto it a greater good for him. Lo, Allah is Forgiving, Responsive. (42:23)

And whoever disputes with thee concerning him after the inspired knowledge which has been given unto thee, tell him, "Come, let us call our sons and your sons; our women and your women; and ourselves and yourselves; then let us pray and invoke Allah's curse upon those who lie." (3:61)

Hold fast to the Rope of Allah, all of you together and do not diverge. (3:103)

Be careful of your duty to Allah and be with the Truthful. (9:119)

Lo, this is My Straight Path, so follow it and do not follow other ways or else you will diverge from His way. (6:153)

O you believe, obey Allah and obey His Messenger and those amongst you who are give supreme authority (by Allah). (4:59)

Whoever opposes the Prophet after the guidance has been made manifest unto him and follows any path other than the path of the true believers, We will turn him towards that unto which he himself has turned, and We will expose him to Hell and a bad journey it will be. (4:115)

(O Prophet) Lo! thou art a warner and for every community there is a guide. (13:7)

Guide us in the Straight Path: The Path of those whom Thou hast blessed... (1:6-7)

They are those whom Allah has blessed among the prophets and the verifiers, the martyrs and the righteous. (4:69)

They (i.e., prophets and Imams) do not say anything until He orders, and they act (in all things) by His command. He knows what is before them and what is behind them and they (i.e., those saints) offer no intercession except for anyone whom Allah accepts, and they are in awe and reverence of His (glory). (21:27-28)

Verily your master is only Allah, and His messenger and those among the believers who establish worship and pay the poor due while they are bowing down in prayer. (5:55)

And lo! Verily I am the Most forgiving towards him who repents and believes and does good and then follows the guidance. (20:82)

O you who believe, enter into peace, all of you, and do not follow the footsteps of the Satan. (2:208)

Then, on that day, you will be asked concerning the blessing. (102:8)

O you Messenger, convey what has been revealed unto you by your Lord, for if you do not do so, you will not have conveyed His message at all. And Allah will protect you from the people. Lo! Allah guides not the disbelieving folk (5:67)

This day have We perfected for you your religion and finalized Our blessing upon you, and We are pleased that Islam be your religion. (5:3)

A questioner asked for the inevitable punishment to befall the disbelievers which no one can avert. (70:1-2)

And when your Lord brought forth from the lions of the Children of Adam their seed, and made them bear testimony about their souls (He asked):"Am I not your Lord?" They said: "Yes, we bear witness." (7:172)

Or are they jealous of those men because of that which Allah has bestowed upon them in His bounty? (4:54)

None touches (the depth of meaning of Quran) save the purified ones. (56:79)

No one knows its interpretation except Allah and those who are firmly ground in knowledge. (3:7)

Ask the people of Reminder if you do not know. (21:7, 16:43)

Source: al-islam