Assalamualaikum ustaz. What is the ruling if I only state “I’m performing the Zohor prayer” for my intention?
Waalaikumussalam wrt. wbt.,
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
Basically, intention means remembering the purpose of action when one is beginning the act. According to the author of the book Fath al-Qarib, the intention is defined as: “Intending to do something followed by the action. And the place for intention is in one’s heart.” 
Intention is one of the valid conditions of every worship. This is based on the hadith of the Prophet PBUH:
إِنَّمَا الأَعْمَالُ بِالنِّيَّاتِ
“(The value of) an action depends on the intention behind it.” 
To make a prayer valid, a person must include an intention during takbiratul ihram and be aware of the purpose of prayer when performing takbir and remember the types of prayer and their obligations. Whilst for the intention to pray, it isn’t conditioned to verbalize it. 
According to madhhab Syafie, it is sunnah to utter or verbalize the intention of prayer before the takbir, so that the tongue guides the heart, avoid doubts and is not too far from scholars who issue a fatwa of its obligation. 
The final opinion in madhhab Syafie also stated that the validity of a person’s prayer is in his heart without verbalizing it and this is the opinion of the majority of scholars. Thus, in this matter, according to Imam al-Nawawi, if a person sets an intention in his heart to perform the Zohor prayer while his tongue mistakenly said Asar, hence, his Zohor prayer is considered valid. 
Coming back to the above question, we cite the statement of Syeikh Hasan al-Kaf who said: “It Is not obligatory to set the intention to idafah (stating it is for) Allah SWT, intention that specifies the number of rakaat, the intention to face the qibla, ada’an intention (current prayer or prayer in its time) and qadha’an (replacement), for all of these is just sunnah.” 
This only applies when one is praying alone, however, if it is a prayer performed in congregation, then it needs for the intention to be a makmum, in congregation or following the imam. He further added:
“If the musolli (person praying) is a makmum, then it is obligated for him to set the intention to pray in congregation or follow the imam or become a makmum. If he doesn’t set the intention to perform the prayer in congregation then he purposely waits (to follow the actions of the imam) for a duration of one requisite of prayer, then his prayer is invalidated and it is obligatory to set the intention (to be a makmum) during takbiratul ihram.” 
Some scholars obligate the intention during the takbiratul ihram, however, the final opinion stated that it is still valid but makruh to delay the intention until the middle of a prayer for he disregards the advantages of praying in congregation.  For Friday prayer, it is obligatory for the makmum to set the intention during takbiratul ihram, for one of the valid conditions of Friday prayer is to pray in congregation. 
However, for a makmum who is doubtful as to whether he has set the intention as a makmum or not, then he can renew his intention without invalidating his prayer.
Although the akmal (best/perfect) is with the existence of qasad, ta’arud and ta’yin as cited in the book Safinah al-Naja.