To show you how whacko a husband can be when his wife says he's having a baby, Tommy John of the Los Angeles Dodgers promised his beloved, Sally, he'd hit a home run for her. The mood might have moved the romantic fool to tell Sally he'd carry her to the top of Everest. But, no. He promised the impossible. A home run.

In a dozen major league season, John established himself as a bona fide 160 hitter. His strength was certified by a total of 14 extra-base hits. Before his wife's announcement, John had hit three home runs, but the last was in 1968, when both the world and Tommy John were very young.

So the other day, when John it one into the leftfield seats here against the Cincinnati Reds, he settled into his home run trot and looked for Sally in the stands.She was behaving the way women do whenever a romantic fool actually delivers on a promise made in passion.

"She was jumping up and down, waving her hands, screaming and hollering," John said. "I thought she was going to have the baby right there."

There are good times for Thomas Edward John, 34, the only lefthanded pitcher who wins games because of his right arm. Doctors three years ago took a tendon from his right arm and sewed it into his left elbow. Then they told him never to throw a baseball again. A lot of guys with bats in their hands wish Tommy John had paid attention to those doctors.

Besides demonstrating his power against the Reds, the pitcher allowed baseball's best-hitting team only two hits in a 4-0 victory. The shutout, the 32d of his career, gave John a seven-game winning streak and raised his won-lost record to 13-4 while lowering his earned-run average to 2.74. All of it moved Tommy Lasorda, the Dodgers' manager, to bliss.

"Tommy John ought to be an example for everybody in this country," said Lasorda. "The doctors said he'd never pitch again. But because of faith in God, a lot of hope and a lot of desire, you see Tommy John out here pitching better than ever."

And that's not all.

"He's a tremendous family man, a tremendous Christian, a tremendous person," said the tremendously enthusiastic skipper. "I want to feel like I'm a father to these guys, and, believe me, it is an honor for me to have such an outstanding human being on this team."

Unless all of the evidence for usually reliable witnesses is wrong. Tommy John is brave, reverent, courteous, kind, obedient and helps old Reds across the street. Out of the farm land of Middle America - Terre Haute, Ind. - where he was a fine basketball player, John is an open and engaging personality in a game where malcontents grow famous. For the movie, we'd get Jimmy Stewart to play John.

In the dugout today, a fan asked John to autograph a picture of a baseball player in 1890s costume. "Now, that's when it was really hardball," John said, smiling. "No hair dryers then." Pause. "But he' couldn't play for Vern Rapp. The St. Louis manager, Vern Rapp, doesn't like mustaches.

The home run, Tommy, how'd you do it? "I want to thank Bowie Kuhn for pumping up the ball this season," he said.

And the last home run, back in '68? "That was off Catfish Hunter. Then the word got around and . . ." Obviously, pitchers decided to throw John no more home run balls.

On July 17, 1974, John destroyed the medial lateral ligament in his left elbow throwing a fast ball in Montreal. Surgery was done in September. His pitching arm was in a cast 16 weeks. The first thing he did when the cast came off was to play catch - with Sally.

"I never had one doubt that I could pitch again," John said.

"What about the doctors?

"I believed if the good Lord wanted me to pitch again for the Dodgers. I would. And if he didn't, I wouldn't and I wouldn't worry about it. Maybe He had something else in store for Tommy John and his family."

Which is not to say John sat on the beach and waited for The Big Relief Pitcher in the Sky to bail him out.

The surgery had traumatized the ulnar nerve in John's left arm. The result was a grotesque drawing up of the muscles, causing his hand to become clawlike. "No way he could even hold the ball," Lasorda said.

To build those muscles, to prevent atrophy, John squeezed Silly Putty. He put a rubber band around a cylinder, then worked one finger at a time against the grip of the rubber. The Dodger trainers used a sound-wave machine, aimed at his palm, to make the muscles work involuntarily. John's arm was massaged every day - and he threw baseballs every single day, either on the sidelines or in batting practice, from the time the cast came off until he returned to the big leagues last season.

"Even when Tommy couldn't see the light at the end of the tunnel, he believed there was a light," Lasorda said of the rehabilitation.

John was 13-3 when the arm came apart in 1974 and was 10-10 last season. "The last fourth of the year, I was throwing as well as I ever had," he said. And he's been that good in this season of Dodger heaven.

His fast ball has been caught at 88 miles per hour. "That's not bad," John said. "Tom Seaver is happy at 93."

Most important, John again is the master of deceition the mound. "After a year and a half not facing major league hitters, you forget how to get them out." He remembers now.

It's done mostly by throwing the ball precisely where he wants it. "Tommy throws to an area this big." Lasorda said, his hands forming a circle the size of a cantaloupe. "And he hits it low and away."

Testimony from Johnny Bench, who hits home runs more often than once in nine years: "Tommy John drives me crazy. I always feel like I should take a three-iron up there."