Football players Husain and Hamza Abdullah are taking the year off from the NFL to make a pilgrimage to Mecca and connect with fellow Muslims around the country. (7:46)

Husain Abdullah should not have received a 15-yard unsportsmanlike penalty after dropping to his knees and bowing in prayer following a 39-yard interception return for a touchdown during the Kansas City Chiefs' 41-14 victory over the New England Patriots on Monday night, the NFL said Tuesday.

According to Rule 12, Section 3, Article 1 (d), "Players are prohibited from engaging in any celebrations or demonstrations while on the ground."

"However, the officiating mechanic in this situation is not to flag a player who goes to the ground as part of religious expression, and as a result, there should have been no penalty on the play," NFL spokesman Michael Signora said.

Abdullah, a devout Muslim, took to Twitter to thank fans Tuesday.

I appreciate the overwhelming love and support flowing from all over the world. #Peace — Husain Abdullah (@HAbdullah39) September 30, 2014

The Council on American-Islamic Relations, a civil liberties and advocacy organization, issued a statement early Tuesday asking that the NFL take steps in response to the penalty.

"To prevent the appearance of a double standard, we urge league officials to clarify the policy on prayer and recognize that the official made a mistake in this case," CAIR spokesman Ibrahim Hooper said.

After Monday's game, Abdullah told reporters that he thought the referees were flagging him for the slide, not prostrating in sajdah -- a common Muslim practice.

"For me, I just got a little too excited," Abdullah said, according to the Kansas City Star. "I think it was for the slide."

Chiefs coach Andy Reid acknowledged as much when Abdullah came to the sideline after his pick-six gave Kansas City a 41-7 lead early in the fourth quarter.

Chiefs safety Husain Abdullah is a devout Muslim who said if he ever scored a touchdown he was "going to prostrate before God in the end zone." Denny Medley/USA TODAY Sports

"He said, 'You can't slide,'" the sixth-year free safety said.

Abdullah played for the Minnesota Vikings from 2008 to '11, then took a year off to make a pilgrimage to Mecca.

He said if he ever returned an interception for a touchdown, the celebration would be automatic.

"If I get a pick, I'm going to prostrate before God in the end zone," he told reporters, according to the Star.

Reid didn't agree with the call at the time.

"When you go to Mecca," he said, referring to the end zone, "you should have the privilege to slide anywhere you want to slide. We have two priests in here. I think they will vouch for me."

Indeed, there were two pastors sitting in Reid's postgame news conference.

The unsportsmanlike conduct penalty touched off a firestorm of controversy on social media, with many wondering how it was different from players dropping to one knee in Christian prayer.

Abdullah is in his second year with the Chiefs after spending an entire season away from the game. He decided that, in the prime of his career, he would join his brother Hamza -- who also was playing in the NFL at the time -- to make a pilgrimage to Mecca. The fifth pillar of Islam is the hajj, the pilgrimage that all Muslims are supposed to make once in their lifetime.

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Abdullah, who also fasts during Ramadan, told the Associated Press in an interview last year the brothers wanted to make sure they did the pilgrimage while they still had the health and means to go.

In the case of Hamza, it proved costly. He never got a shot to return to the NFL.

Husain Abdullah said he didn't expect any repercussions from his penalty Monday night, least of all from his coach. After all, it was Reid who gave him an opportunity to work his way back into the league after he had stepped away.

"I'm pretty sure he understands who I am, what my faith is," he said. "And again, I think the prostration is all right. It's the slide. Come to a full stop, get down, make the prostration, get up and get out."

Information from ESPN's Ed Werder and The Associated Press was used in this report.