be vigilant

References in classic literature ?
Bucket came out again, exhorting the others to be vigilant, darkened his lantern, and once more took his seat.
Be faithful, be vigilant, be untiring in your efforts to break every yoke, and let the oppressed go free.
But the Emperor restores his weapon, and, with that smile which won all hearts, says, pointing to a high rock whereon a crow happens to be sitting, "Be brave, be vigilant, and remember that from yonder Pyramid generations are beholding you," and with these memorable words he vanishes, leaving the grateful soldier bolt upright, with his hand at his temple and deathless devotion stamped upon his youthful countenance.
Either way, it's not a one-off job - you'll have to be vigilant for new growth to keep the problem under control.
Farmers' Union of Wales, senior policy officer Dr Hazel Wright said: "We are advising members to be vigilant and consult their veterinarian surgeon should they have concerns about their poultry being infected with avian influenza.
We want to remind people in the area to be vigilant and to ensure properties are secure.
I am therefore asking that local residents be vigilant and report any suspicious persons hanging around the Manor Road area to the Valleys NPT, at Holmfirth police station, via 101.
I am sure he is aware that Israel shares a border with Syria and while the Israelis appear to be vigilant in that regard, trouble could escalate into their country, as has happened with Syrians attempting to escape to Lebanon and meeting an untimely death.
Police patrol officers are stopping and talking to lorries parked up in dual carriageways lay by to urge them to be vigilant.
Yes, we are linking the grenade attack to the threats that have been issued by Shebab and that is why I am appealing to city residents to be vigilant and cooperate with our officers," Antony Kibuchi, provincial police chief for Nairobi, said.
I would like to ask Echo readers to be vigilant on our behalf.
We will still have to be vigilant - even more vigilant - in the coming days about the international terrorist threat.