Issues that weren’t mentioned by The Imams(as)?

al-Shaykh Yusuf al-Bahraini writes: 

“And from them (the doubtful matters) is whatever there is no principle for, as you know, and its ruling is to refer back to them (the Imams), otherwise, [it is obligatory to do] tawaqquf and ihtiyat (caution).”

📚al-Durar al-Najafiyah, V1, P184

Ammar As-Sabati reported that Imam As-Sadiq (as) said: “Everything is clean until you know (with certainty) it is unclean. If you have gained the knowledge about it, then it has become unclean, but as long as you do not know it, you have no obligation. 

📚Wasa’il-Ush-Shia  V3, P467

Abu Basir reported that he asked Imam As-Sadiq (as): “We are dealing with matters, which we do not know in the scripture of God nor in the custom (of the prophet). Do we form our own opinion about it?” He said: “No, if you are right, you will not be rewarded and if you are wrong, you have lied about God.” 

📚Kitab Al Kafi  V1 P56 (Dar Al Kutub Al Islamiyah)

Ja’far As-Sadiq (a.) reported that prophet Muhammad (s.) said: “My nation is excused from nine things: from that, which is ignored and forgotten, from that, which they were compelled to do, from that, which they do not know, from that, which they are not capable of, from that, which they were in need of, from evil omen, from envy and from pondering about that which is whispered in the creature, as long as man did not express it in words through his lips.” 

📚Al Fusul V1 P638