By magnifying the Law of Moses (which no-one other than himself had ever been able to keep perfectly) He was showing his audience, especially the Pharisees and those who thought they ‘had it sorted’ the utter impossibility of ‘entering into the kingdom’ by Law keeping.
‘How then can anyone be saved?’ his disciples asked later. ‘With man this is impossible, but with God all things are possible’ he replied. An enigmatic response that He did not elucidate further at this time. It was left to those writing after His death for the inspiration to explain it. [See New Covenant]