To answer this question you only need to know that there is a bible.
And it can be whichever bible you are familiar with.
Question:
What is the single MOST IMPORTANT teaching in the bible?
According to the bible (and coming directly from the highest authority) it is Marc 12:28 - 31.
"28 One of the teachers of the law came and heard them debating. Noticing that Jesus had given them a good answer, he asked him, “Of all the commandments, which is the most important?”
29 “The most important one,” answered Jesus, “is this: ‘Hear, O Israel: The Lord our God, the Lord is one.a]">[
a] 30 Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.’b]">[
b] 31 The second is this: ‘Love your neighbor as yourself.’c]">[
c] There is no commandment greater than these.”"