Authenticity of the Hadeeth “The sleep of the fasting person is worship”

This hadeeth is not saheeh, and it is not proven from the
Prophet (peace and blessings of Allah be upon him). 

Al-Bayhaqi narrated in Shu’ab al-Eeman (3/1437) from
‘Abd-Allah ibn Abi Awfa (may Allah be pleased with him) that the Prophet
(peace and blessings of Allah be upon him) said: “The sleep of the fasting
person is worship, his silence is tasbeeh (glorification), his du’a
(supplication) is answered and his good deeds will be multiplied.” Its isnad
(chain of narration) was classed as weak by al-Bayhaqi who said: Ma’roof ibn
Hassan (one of the men in the isnad) is da’eef (weak) and Sulayman ibn ‘Amr
al-Nakha’i is weaker than him. Al-‘Iraqi said in Takhreej Ihya’ ‘Uloom
al-Deen (1/310): Sulayman al-Nakha’i is one of the liars. It was classed as
da’eef by al-Manawi in Fayd al-Qadeer (9293) and it was mentioned by
al-Albani in Silsilat al-Ahadeeth al-Da’eefah (4696) who said: It is
da’eef. 

What the Muslims should do in general – and this applies even
more so to khateebs and da’iyahs (callers to Islam) – is to verify reports
before attributing a hadeeth to the Messenger of Allah (peace and blessings
of Allah be upon him). It is not permissible to attribute to him anything
that he did not say. He (peace and blessings of Allah be upon him) said:
“Telling a lie about me is not like telling a lie about anyone else. Whoever
tells a lie about me deliberately, let him take his place in Hell.” Narrated
by al-Bukhari (1391) and by Muslim in the introduction to his Saheeh (4). 

And Allah knows best.