The knock comes on the door of a simple gate at a Catholic church in Baghdad.

A recent newspaper story tells about Sister Pauline, who opens the door and never knows what she will see.

Sometimes, she meets a parent whose spouse was killed in a bombing and who wants to leave the children with her.

And so, this faithful nun, age 71 and suffering from cancer, gives the children a home at St. Hannah Church and Orphanage.

Reading about this woman’s stunning faith reminded me of the knocks that come on the doors of our own hearts.

God tiptoes toward us and asks to be invited in. But sometimes the heart is crowded with the rickety furniture of old regrets:

“I should have married John. I should have taken that job in Boston. I should have invested in real estate.”

With so many regrets, there is no room for God.

The heart may also be crammed with longings. “One day, when I am rich…when the kids are grown…when I get that promotion…when I finally win the lottery…”

And the static from these dreams is loud, and the knock goes unnoticed.

Some hearts are scarred with wounds that have never healed. These hearts drown out God’s voice with the “if only” litany.

“If only my husband hadn’t left me,” “If only I had gone to college” and “If only my boss appreciated me.”

Other hearts are dark caves of worries and fears, and the mantra is “What if?”

“What if the avian flu strikes the U.S.? What if the doctor’s office calls with a bad report?”

The fears are prancing around, snarling and growling, and they block out the knock at the door.

God stands outside, just waiting for a sign from us. He doesn’t push his way in and insist that we make room for him.

Instead, if we utter just the slimmest prayer or indulge in the smallest act of faith, He will make his home in our hearts.

We awaken at 3 a.m. with the realization that it is time to leave behind a life-sapping job, take on a new ministry at church or get off the merry-go-round of bad relationships.

But if we’re not ready to hear His voice, we just turn over and go back to sleep.

Some hearts have huge walls around them and come with built-in security devices, which result from years of cynicism.

If God tries to edge close to these hearts, He will have to chip his way through the heavy armor of intellectualism and pride.

“Religion? That’s for kids. I’m far too sophisticated for that stuff.” Oddly, though, the person has faith in things like the brakes on his car working and the medicine his doctor prescribed, but not in God.

Often we know that God is trying to get to us, but we are overwhelmed by our relentless schedules.

“Buy paper towels; call mom and dad; pay the water bill; take the dog to the vet; and schedule the dentist’s appointment.”

In the midst of our frantic pace, we don’t notice the gifts God sends each day.

A mockingbird singing its heart out atop a nearby tree. A cloud adorning the sky like frosting on a giant cake.

God knocks, but we are enslaved to entertaining ourselves with TV, movies, shopping and bar hopping, and we have no time.

We tell God to come back later.

“Later, after I’ve graduated from college, then I’ll figure out the God thing. Or later, after the kids are out of school, and I have more time to read Scripture. Or after I’m retired, because this job is draining my energy.”

Truth be told, we may be afraid to hear God’s voice because He might ask us to do things we’re not ready to do.

What if God urges us to let go of some poisonous relationship that has been wearing us down for years? Or tells us our job is wrong for us? Or that our addictions have to go?

“Oh, no, don’t tell me I have to give up…overeating, drinking, recreational shopping, TV, sports, on-line gambling. Don’t tell me I have to ditch this boyfriend who has been making me miserable for years. Please, God, if those are your messages, stay away from my door!”

Then comes the image of that nun in Baghdad, who certainly has plenty of excuses to avoid hearing God’s voice.

“Leave me alone, God! I’m 71 and I’m tired,” she might have said. “Or I have cancer, and I’m too sick to take in more children.”

Still, she goes to the door, opens it and deals with the messages that await her. First, though, she has to hear the knock.

She has to empty her heart of obsessions, worries, regrets and longings. She has to put aside her relentless schedule. Most of all, just like us, she has to make room for God.