2:32Al-Baqara

"The Quraish said to the Jews: 'Give us something that we can ask this man about.' So he said: 'Ask him about the Ruh.' So they asked him about the Ruh. So Allah Most High, revealed: They ask you concerning the Ruh. Say: The Ruh is one of the things, the knowledge of which is only with my Lord. And of knowledge, you have been given only a little (17:85). They replied: 'We have been given immense knowledge, we were given the Tawrah, and whoever has been given the Tawrah, then he has indeed been given a wealth of knowledge.' So the following was revealed: Say: 'If the sea were ink for the Words of my Lord, surely the sea would be exhausted (before the Words of my Lord would be finished.) (18:109)'"

"The Messenger of Allah (saas) used to say: 'Allahummanfa'ni bima 'allamtani, wa 'allimni ma yanfa'uni, wa zidni 'ilman, wal-hamdu lillahi 'ala kulli hal, wa a'udhu billahi min 'adhabin-nar (O Allah, benefit me by that which You have taught me, and teach me that which will benefit me, and increase me in knowledge. Praise is to Allah in all situations, and I seek refuge with Allah from the torment of the Fire).'"

"I will not teach you anything but that which the Messenger of Allah used to teach us. He said: 'Allahumma inni a'udhu bika min al-'ajzi wal-kasali, wal-bukhli, wal-jubni, wal-harami, wa 'adhabil-qabri, Allahumma ati nafsi taqwaha, wa zakkiha anta khairu min zakkaha, anta waliyyuha wa mawlaha. Allahumma inni a'udhu bika min qalbin la yakhsha'u wa min nafsin la tashba'u wa 'ilmin la yanfa'u wa da'watin la yustajabu laha (O Allah, I seek refuge in You from incapacity, laziness, miserliness, cowardice, old age, the torment of the grave. O Allah, make my soul obedient and purify it, for You are the best One to purify it, You are its Guardian and Lord. O Allah, I seek refuge in You from a heart that is not humble, a soul that is not satisfied, knowledge that is of no benefit and a supplication that is not answered.)"

"We were with the Messenger of Allah (ﷺ) and we did not know anything, then the Messenger of Allah (ﷺ) said to us: "Every time you sit (in prayer), say: At-tahiyyatu lillahi was-salawatu wat-tayyibat, as-salamu 'alaika ayyuhan-Nabiyyu wa rahmatAllahi wa baraktuhu. As-salamu 'alaina wa 'ala 'ibad illahis-salihin, ashahdu an la illaha ill-Allah wa ashhadu anna Muhammadan 'abduhu wa rasuluhu (Allah compliments, prayers and pure words are due to Allah. Peace be upon you, O Prophet, and the mercy of Allah (SWT) and his blessings. Peace be upon us and upon the righteous slaves of Allah (SWT). I bear witness that none has the right to be worshipped except Allah and I bear witness that Muhammad is His slave and Messenger)."

We did not know what we should say when we sat during prayer. The Messenger of Allah (ﷺ) was taught (by Allah). He then narrated the tradition to the same effect. Sharik reported from Jami', from AbuWa'il on the authority of Abdullah ibn Mas'ud something similar. He said: He used to teach us also some other words, but he did not teach them as he taught us the tashahhud: O Allah, join our hearts, mend our social relationship, guide us to the path of peace, bring us from darkness to light, save us from obscenities, outward or inward, and bless our ears, our eyes, our hearts, our wives, our children, and relent toward us; Thou art the Relenting, the Merciful. And make us grateful for Thy blessing and make us praise it while accepting it and give it to us in full.